Originally Posted by Isaac Springsong
Long Rest should be available in dungeons, just with a risk. PKM has a wonderful system for this, literally forcing you to find a space to build a small camp and a significantly increased chance of a random encounter. Additionally, it will pay *huge* dividends down the road as characters get more abilities and higher level spells come online. Leomund's Tiny Hut is a staple spell in any Wizard's spellbook for this exact reason, Mords Magnificent Mansion, etc.

+ 1
I really like this idea, it adds a lot of niche use for those spells and it makes long term dungeon delving still possible for a price of increased risk.