As for my estimates of a national recovery period, I'd wager 2-3 years until we hit the bottom. Then it'll be a gradual increase up from there.
By the time 1-2 years have passed, most of the dangerous subprime ARM loans will have reset (
pretty graph). Thus, the people who have mortgages that they can't afford will hit the point where they realize that they cannot afford their homes. After that it'll take 6-12 months for the homes to go on the market (willingly or through foreclosure). Thus, the flood of homes for sale without many buyers (
polls say they definately are not buying any time soon) will last 2-3 years. Although, you can see that other ARMs will keep resetting for a bit longer, and even people with fixed loans may have problems too.
I really don't know how long it'll take to recover what was "lost". We really have to fall much further than I expect we will fall until we reach a point where housing is truely affordable. But, instead of falling that far, I think we will instead have massive inflation catch salaries back up. So, prices will probably stabolize in 2-3 years and possibly slowly rise, but at a rate lower than inflation. That will happen until we reach parity, or until there is another senseless boom. To give that a rough estimate, I'd say 10 years for everything to return to levels where houses are affordable.