Sorry if I've missed someone else's post on this already; I just noticed that there is already a second page to the thread.
Mandating down time so that characters age between exploits is fine for elves, and even for dwarves. I'm guessing humans will be our benchmark, here, so they'll be fine, too.
Half-orcs and other 'short-lived' raced get royally hosed in this plan.
Skipping ten years of disinteresting campaign time, what do all want to do now that you've aged a bit and the world has moved on?
Halfling Rogue: hide out in the Inn I opened so the others won't find me. It's taken me all this time to earn back the other hobbits' respect.
Human Paladin: Select a squire from amongst my parishners to serve as a squire, for though my mind and faith have strengthened, my back has not.
Elven Wizard: What? Time to get up already? Didn't we just rid the world of that menace a decade or so ago? Alright, so be it; I'll just put the finishing touches on the longsword I've been enchanting and I'll be ready to go before the next blue moon.
Dwarven Fighter: We'll now that I'm an adult and now longer have to seek the clan's permission, I suppose we'll be off! But first, we feast!
Half-orc Barbarian: I'm the tribal elder now. I can't go anywhere! Leastwise, not without a walking stick.
The thing about levelling up in a quick hurry is that most heroic figures of legend in our own world have finished their conquest before they turn thirty. Those who haven't likely never will.
Boy, that's depressing coming from a 31 year-old college student who has yet to even conquer Northern California.