And in 3E it is a matter of a day or two for a first level Wizard, perhaps a little longer for a more combat-oriented class.Because in six hours, with absolutely no treatment, he's at perfect peak fighting form.
In any event, as I've posted before, I think that the short rest and healing surge mechanics are quite distinct from the extended rest mechanics. As many have posted, you can alter the latter if you wish without changing the dynamics of combat and in-combat healing at all (eg using the approach in the Advanced Players Guide). Or you can just narrate it the same as you do recovery from a short rest - that is, as grit and determination.
This really can't be stressed enough.Though of course from the perspective of an encountard or 4E designer, this all doesn't matter. Once a character is stabilized, he won't die because his allies will bring him back to full fighting force in no time, using medical aid, potions, spells or wands of cure light wound. So from that perspective, the "verisimilitude" concessions created by alternative healing models are meaningless in actual play, and thus not required.
If the complaints are really about extended rests, just add the following class feature to Clerics: also automatically learn the 1st level ritual Heal All Wounds, cost free, no skill check required, 10 minutes to perform, after an extended rest the target recovers all healing surges. Now the game plays no differently except every party needs a cleric (or some other ritualist who has payed to learn this ritual).
We have now recreated the verisimilitude of 3E healing.