AbdulAlhazred
Legend
I "stop" the party from taking extended rests in two ways:
1. I don't design all encounters to be challenging the PCs to their utmost. No more 3e encounter design. A lot of encounters are just wearing them down a bit. Remember adventures in AD&D?
2. More importantly, extended rests have to make sense in-character. Why doesn't the party take an extended rest in the depths of a dangerous cave complex? Because nobody would do that--it would be foolish. I demand that my players play with a bit of verisimilitude. I don't need artificial time tables (though I occasional use in-story time tables), because the players need to play their characters in a way that makes sense.
It simply does not occur to anyone I play with that they should play such a meta-game. I give them fun encounters and they play it cool. If someone dies, well, at least there is a little drama to it.
I think really, we all people who have enjoyed 4e just want to see even better stuff. I'm convinced there is a perfectly reasonable game at the intersection of our desires. I think now is getting to be a good time to see what you have WotC! C'mon. Just because some people are going to complain...