Note: This was originally a forum post, at Garthanos's suggestion, I decided to put it up here. If you'd like to see it in context, it's here.
Disclaimer, I'm one guy. I'm not the elected speaker for my side or anything fancy like that, and I'll probably miss something. Anyone else who hates the 5MWD, feel free to chime in.
First, we need to look at what the 5MWD is. This would seem straightforward, and no one really stops to explain it anymore, not beyond a sentence or two. They probably should, though, because there are two distinct problems that are both referred to as the 5MWD. They're not dissimilar, and they tend to both occur during a good example of the 5MWD, but they are distinct.
The first problem is when the party is pressured to stop and rest before the dungeon is complete, often resulting in running back to town or making a camp in a defensible position. This is an issue because it's just so narratively jarring. Camping in a dungeon isn't really a part of the thematic sort of stories that D&D is built from. The only story I can really think of where this happens at all is LotR, when they camp in Moria, and in Moria, they don't rest because they fought too many orcs, they rest because it takes days to get from one end of that hellhole to the other. In fact, when the heat starts to come down on the party, holing up is the last thing on their minds. But the mechanics of D&D don't really encourage this sort of story. In D&D, whenever you can get away with sleeping for a few hours, it's best to do it. Sleeping restores your resources, and the amount of resources you have remaining has a pretty large impact on your chances of survival. In D&D, reasons to press on instead of sleeping if you can must come entirely from the DM and/or the players. If you don't keep on top of providing them, you end up playing Dungeon Camper, and Dungeon Camper is a weird game that no one actually likes, they just put up with it because the alternative is probable character death.
The second problem is balance. When you have some classes using daily abilities and some using at-will or encounter abilities, you have to have a certain amount of encounters in the day in order to keep them roughly in line with each other. Too many encounters and the casters can't pull their weight, too few and they get overwhelming. This is a problem for two main reasons. First is that the party mechanically benefits from going under this number. The fighters and rogues don't get any worse, but the wizard and cleric get better. It's in the party's interest to rest early if they can get away with it, as I mentioned before, so this puts the DM on constant Rest Police Duty. The second is that building for a set number of encounters per day, consistently, is a major restraint on the types of adventures you can have.
These things are called the 5-minute workday. Sometimes they're called the 10 minute workday, or the 15 minute workday. The exact number of minutes doesn't matter. It's named for the observation that even if it takes some time at the table, for the characters, combat goes really quick, just a few seconds to a minute tops. A party that enters the dungeon at 8am can find themselves used up for the day by 8:15 or 8:30.
Now, if you don't experience these issues yourself, and you're just hearing about them for the first time, I'm sure you're just chomping at the bit with all the advice I'd need to banish these problems forever. But it won't be anything I haven't heard before. I'll go over some of the more common "fixes" and tell you why the issue isn't resolved for everyone forever.
One we get a lot is "The world doesn't stand still while players rest, not in my campaign!", as though the rest of us have never actually considered the difference between a campaign world and a battlemat. For bonus points, some people like to tout this old Gygax quote, "You cannot have a meaningful campaign if strict time records are not kept." Usually the point this is getting at is that there's a lot of things in the world that can interrupt characters from sleeping, and that adversaries will not necessarily just let this camping happen. This usually seems to assume two things that aren't necessarily going to be true, though. First is that "the enemies" are going to be able to do something to stop the players, and the second is that they will. Now, when you're fighting intelligent humanoids, this is generally going to be true. I'd be surprised if a squad of hobgoblins didn't toss some grapping hooks into the players makeshift barrier and pull it down. But some foes lack either the ability or the will to break up a camp. Zombies might want to get the players, but a decent barricade, as from furniture piled against a door, can hold them off. Even if they could get through eventually, having someone on watch ensures that the PCs will have enough warning to get up and be ready. Wild animals, like wolves, aren't going to have the will. They might want to eat the PCs, but real predators aren't stupid or suidicial. A pack of wolves isn't going to attack a group of people who have a sentry and a fire. They might stalk around and wait to catch someone when he goes to take a leak, but they aren't going to rush the camp. That's just too much risk for a meal, unless the PCs are the only other living things in the whole wood. But hey, all I have to do, as the DM, is stick to only ever pitting the PCs against intelligent, humanoid foes, right? I mean, Indiana Jones sucked, who'd ever get excited about exploring an abandoned temple, for something as lame as treasure, right?
The next piece of advice we get a lot is, as you might expect, also time-related. It usually comes like this, "Well, I guess they can rest if they want...if they want the goblins to kill all the hostages!" You can substitute whatever other sort of quest failure you'd like to, the intent is the same. The idea is that if the PCs are kept on a strict schedule, with clear consequences for dallying, then they'll keep the proper pace. And they will, it's true. All I'd have to do is make sure that every mission is on a strict time crunch. 5MWD aren't about taking huge amounts of time, so it does have to be a strict crunch. The 5MWD doesn't turn a 1 day dungeon into a 5 year dungeon, it turns a 1 day dungeon into a 2 or 3 day dungeon, on average. So deadlines like "Better get the Amulet of Blah back here by the end of the month!" are meaningless. We need to stick to "And if you don't find the Snowlight Flower by midnight tomorrow night, the Prince will die!" Now, I'd like to stress that there's nothing wrong with this sort of adventure. Hell, they can be a lot of fun! But they aren't the only type of adventure I ever want to run, and if they are, the deadlines start to feel contrived and lose their urgency. The first prince you have to save by midnight is fun, but the seventh time in a row that you hear, "We have to do X, and fast!" you start to feel like you're in a rerun of the Justice League cartoon.
The final piece of advice I'll cover in this post is a lot like the first and second, but it's dirtier, so I'm making it separate. This is when people say that you should invent circumstances to screw over characters that try to rest before you want them to. This is the type where the zombies suddenly have a Graveborn commander that wasn't in the cards before and helps them tear the barricade down. It's the type where the orc bandits that no one knew were there rape and pillage the village while the players were away, because they took an extra day. In other words, this advice is that if you don't have something prepared to force players to dance to your tune, make it up. I hate this advice, though I've recieved it many times. I hate it because what it amounts to is saying that I should just use in-game circumstances to punish players who don't play how I want them to play, usually continuing the abuse until the players will jump before I crack the whip. Control over their own characters is the only real sort of control the players have in D&D, and if I make that control illusory, I might as well just play with myself. At least that way I don't see a jerk when I look in the mirror.
So, to sum up my advice rebuttals, they all absolutely work. If I'm willing to restrict my adventures to a narrow subset of possible adventures, spend a lot of extra time and energy coming up with reasons not to rest, and browbeat my players until they fear my iron fist. At the end of the day, once I've done all that, my reward is a system that needs me to stick to a set amount of encounters per day to have a semblance of balance. And then I get to preserve a system that encourages cowardice instead of bold action, and that uses wildly differing resource recharge systems. The problem here is that I don't like the former and the latter holds no special value to me. So, if I go through a bunch of crap, I can get a turd and a lemon. Wooooo....
I'd rather have a system where if going on is not encouraged, at least going back is not over-rewarded. Going on should be dangerous, but not because while the encounter wouldn't be too bad if we're rested, we're already beat up. Going ahead should be dangerous on its own, whether you've had a good night's sleep or not. I'd rather have a system where I don't have to ensure X encounters or rounds or whatevers per day or adventure or whatever to ensure balance. Personally, I don't tend to have more than 1 or 2 combats in the works per day, when I DM. They're important when they happen, but they aren't constant. I want that to work. And if I decide that we should have more, I want that to work, too.
