Basically, nobody (but me) is planning to pay off their loan. They all expect to sell out and move long before the debt is paid off.
What is happening now of course is the cash-out. That's why the housing market is slumping a bit. People are selling out to move to bumfuk and beyond. One of my coworkers is doing that. His wife owns the mortgage on a 1700 sq foot house she bought in the mid 90s for $135K (before they were married)... she is selling that and buying a 3400 sq' house in Colorado where they are planning to move by the end of the year. She's a nurse, he's a computer tech, they figure they'll end up with cash in the bank and the new place free and clear or with a modest mortgage if they go crazy on counter tops and landscaping. I've looked at the pictures of the development in Colorado... looks like it was designed to lure losers from this market... made my skin crawl... then again I have a couple acres in a "rural suburb" so I'm not following the "core market values".
Me, I'm a throw-back I guess... I've got 4 years left on the 15-yr mortgage I signed up for when I was 19.... and I don't plan to sell the house once it is paid off... though I do plan to grab another mortgage as soon as this one is up, hopefully picking up some acreage in Wyoming or the like.... about when my airplane is finished..... which is way off the off-topic topic.

And there is no way I could've bought my house in today's market. Incomes available to even enterprizing and cocky 19yos haven't gone up nearly as much as house prices... but I was lucky to have hit the market right in the middle of the last slump when everything was cheap.