back to the OP
It can happen that the party run into a tough fight and want to recuperate. bad luck it happened first off. If it happens continuously then either the encounters are so tough they feel they have to go through everything in one hit, or the players are just used to burning everything at once because they know they'll go and rest now. IMHO, without knowing the situation, that doesn't sound like a fun game but different games, different people and no offense meant
IMC, its city based and so we don't often have long dungeon crawls. occasionally the party runs away to regroup, but thats not an issue. they briefly talked about locking themselves into a room in a dungeon to recuperate but they know i will mobilise the intelligent monsters left against them so wisely decided against it. Recently i've been putting them through a series of mini-adventures in quick succession so they haven't had time to rest - its been either now or never (3/4 successful, one got away) and that's been fun to watch (& play i hope)
Where i play, theres one campaign where we do seem to pull back and rest several times before completing the adventure. Personally i don't like it, but the rest of the party will not go forward after they run low on heal spells which I can't really argue with. I don't think the DM has a lot of choices due to the fact its a published AP so we just live with it. the best bits though have been where we can't recuperate and we've had to carry on fighting / running retreat and get that kick from succeeding with no spells, 50% hit points and few items left.
a few weeks ago we took out a bunch of giants (party level 10), the cleric lobbed a flame strike, several heals and a couple of other spells into the mix. Then started talking about going home. At this stage my wizard pointed out that he'd only used 3 spells all encounter (Grease, Summon 3, acid arrow) and he'd quite like to continue. Not boasting but it is all about how you use the spells and i do make a point of trying to use low level spells first and saving the best until last. admittedly the flame strike made a big difference (5 giants affected) so I'm not criticising the Players choice, but its not necessary to use biggest spell, all the time and the blam, blam rest philosophy makes the other character types less useful as it becomes all about the spell casters. Plus its pretty dull....
on 'per encounter' abilities. not sure if i'm that keen on these. IMHO either make them at will - eg give a wizard low level blasts at will if you want him always to do something or force the party to resource manage. I'll leave that discussion to the 4E board though