My wife's first experience DMing was to run RttToEE. We had a party of four dwarves, and by the time we made it to the crater ridge mines, we had four rings of sustenance.
We blitzkrieged through there and earned the party name "Twelve Second (of Bloodshed)" We The party included a Psion/Sangehirn who soaked up all of our damage, a Fighter/Barbarian Mulcher who murdered almost non-stop, a Fighter/Rogue Archer with focus on locks and traps and a Wizard/Cleric who blasted (or dominated) his way through every foe he encountered. We'd blaze through spells and power points as quickly as we needed to, take a nap, do some turn-around, and be back on our way. We probably ended up sleeping eight or ten hours a day through that dungeon, but we also probably finished it in less than ten days game time.
I think that from now on, I might rule that two hours sleep with the ring does everything that eight hour without does, but that the character can't sleep again for at least eight hours after getting up, now matter how quickly they burn through their resources.