If the dungeon is extremely dangerous the party can certainly go in, clear a room expending all resources and then go out and rest for a day, and come back tomorrow. It could take them weeks to clear a dungeon, but they'd be safe. Especially in a game that house rules death to be much, much more severe.
As a player I put alot time into a character, back story, goals, ambitions... if playing in a game where the DM says you are basically going to die, alot, that creates degenerate characters. Why then would a DM punish good characters for wanting to be cautious? Sounds like typical DM vs players mentality and the DM should play hackmaster.
This doesn't change anything. The fault lies at the table. It's one thing for the players to experience a string of bad luck, or barely survive a bloody battle, and decide to retreat to a "safe" place for a rest. It happens from time to time. But there's a difference in doing that, and just abusing the opportunity.
If the members of the gaming group are aware of what is referred to as the "15mwd", then they are aware of when it's being abused. You can call it whatever you wish. I call it an exploit. Whether it's exploiting the rules or lack thereof. But like I said in my earlier post, if that's the way you enjoy playing, so be it. As long as you and your group have fun.
Thankfully, my players enjoy a challenge, play within the spirit of the rules, and would rather not play at all if there weren't any risks of dying. Adventure is about risk. Without it, what's the point? The DM might as well sit each player down, in turn, and tell him/her how he/she has won the game of D&D while they look on with doe eyes, bouncing up and down on the edge of their seat, clapping their hands and yelling, "YAAAY!" Too many these days want easy mode in all things. They neither like, nor want a challenge. But whatever. If that's the way a particular group likes it at their table, more power to them. But those types would be in for a harsh "reality" check at my table, and wouldn't last long. If they did stay, they'd learn to use tactics and stealth, manage resources, and make use of the option to parlay whenever it was relatively reasonable or possible. In other words, they'd learn to be cautious, not just abuse the system and call that being cautious.
Again, thankfully my players don't exploit, but if they did, if I felt they were abusing the "15mwd", then I'd just use similar reasoning (like "being cautious" for example). The living world would simply repopulate the areas they've cleared, call reinforcements, be on alert, and/or the enemies would send patrols out after the players. I could even take away their retreat, have the enemy collapse the cave entrance or some such, and the only way out would be to move forward. It's not a DM vs players mentality, it's just a DM trying to be a good DM by not allowing abuses or exploitation at the table. My players haven't complained. Some of them have complained, however, about the occasional game under certain DMs and players at the local hobby store, in games where they felt like they couldn't die, that they were being coddled, or the rules abused. That may sound elitist, but I'm so thankful, and glad for the opportunity to play with players who, like me, enjoy playing in the spirit of the rules and adventure, in a gritty game that actually challenges them.
"It's the sour and the sweet. And I know sour, which allows me to appreciate the sweet." - Brian Shelby,
"Vanilla Sky"
As to DM vs player mentality, or is it player vs DM mentality? I've played in a game or two where I felt the DM was showing favoritism to certain players, but never one where I felt the DM was trying to kill my character. On the other hand, I've gotten the impression many times, especially reading forums, where a player seemed to feel he was entitled. In some cases, just because he did something every player is encouraged to do (and from my experience, does), like put some thought into his character. It could be the DM showing favoritism, having it out for a player or the group; or it could be the player whose character dies due to unlucky die rolls or series of bad decisions and then blames the DM. Whatever the reason for a DM vs player vs DM mentality, these people shouldn't be playing together. There's either a real issue with the DM or player, in which case they probably shouldn't be playing with anyone til they grow up a little, or the group members are simply incompatible. Thankfully, other than the incident I mentioned where a DM seemed to show favortism for certain players, I've never had any issues, and in those cases, my friends and I simply didn't return for further gaming sessions.
Ultimately, it's up to the DM whether he allows the sort of abuse that leads to the "15mwd", no matter how one tries to rationalize it as otherwise. If the "15mwd" is something that is considered an issue (meaning it's not something wanted or enjoyed) at the table, then the DM and the players at that table possess the tools to avoid the abuses enough that it wouldn't be considered an issue.