So 3E didn't invent the 15-minute adventuring day, then?
No, it didn't. Which is why I...
a) Became somewhat annoyed with the WotC designers when they erroneously blamed the '15-minute adventuring day' on particular features of 3e.
b) Knew ahead of time that you couldn't fix the '15-minute adventuring day' by changing the rules, any more than you could gaurantee exciting encounter design by changing the rules.
The 15 minute adventuring day is a product of a certain tactical situation, namely:
1) That the PC's are the most active and proactive things in the environment or even the only active and proactive things in the environment
2) There is no real time pressure
3) There is any resource whatsoever which is consumable and may require time to replenish whether it is hit points, healing surges, or simply ammo.
Generally speaking, I never have games with 15 minute adventuring days regardless of system because I tend to have proactive villains that will hunt down the PC's with whatever resources that they have or who will themselves replenish and repair using whatever time they are given. This is the lesson of Ravenloft versus other modules. A proactive villain makes a module much more dangerous than one that is passive, and its true whether you are talking kobolds or powerful spellcasters. It's therefore necessary for the PC's to press on while they have the advantage and seize as much of the moment as possible. Likewise, I tend to have a combination of hard and soft time limits. If the PC's don't disrupt the villains enough, bad things will eventually happen. So the PC's have to keep applying pressure to the villains. They can't wait as long as they might like at every oppurtunity. And even without clear time limits, the world around them keeps living. New events keep happening. So, I almost never have 15 minute adventuring days. Those people who tended to have 15 minute adventuring days in 3e would with the same players tend to experience the 4e equivalent unless either they or their players changed their play style.
The 4e equivalent logic is, why risk going into an encounter in the ToH without dailies and full healing surges? The answer is either, 'Because it's not very stylish', or else, 'Why not?'