SAY, YOU BORROWED some money, but promised to pay it all back, with interest, over the next 10 years. Well, now you want lower monthly payments - what do you do? That's right, talk your lender into allowing you to pay it back over the next 30 years instead. Your monthly payments will be lower, but your lender probably won't mind - since there would be a lot more of those payments coming to him.
Or, that's what he thinks. 30 years is an awfully long time - who knows? You might not be even around in 30 years, or maybe your lender will keel over or maybe the dollar will become worthless, or maybe the world will end in 2012. What's important is how much you will have to pay next month, right?
Or you can negotiate to have low payments for the next five years and much higher payments later. In any case, your mission is accomplished - lots of borrowed money now, low payments and who cares what happens later? I certainly don't.