I also want to clarify - while we often had the 15 minute adventuring day back in our long running 3.5E campaign, we had a lot of very memorable encounters during that campaign, so I think the group (myself as DM, and 8 players at the time) was generally satisfied with how things went as we had enough plot, story, NPC interaction, etc in between the encounters that it didn't feel like a 15 minute adventuring day at the table.
Also, while we still have some 15 minute adventuring days in our 4E campaign, it's less common than before. Usually, the players will want to press on after a short rest so they at least have their encounter powers refreshed. So, the group will have a couple of encounters, take a short rest, do some exploring, interact with some NPCs, etc, and then maybe run into another encounter or two afterwards. I've also made use of "Boons" from the DMG2 where you can do something in game that allows a PC to refresh a daily power (i.e., in the second encounter, they defeat the orc sub-boss. So, not only do they get a milestone, but they can pick one daily that they can recharge.) That way, the players feel that they at least have one daily in reserve for that next encounter.
Additionally, back when I played 1E and 2E D&D, we weren't the types that used dungeon crawls a lot. Most of our adventures and encounters were outdoors and in the open. Hence, when the party got banged up, we'd set up camp and heal up until we were ready to go on again. So, it wasn't a matter of getting 20 rooms into a dungeon and then having to retreat back to town to rest and recover.