Oh, I think I understand what you're saying. That as the interest rate goes up and you limit the monthly payment to $1000 then you'll have a situation where the loan would not get paid-off. I don't think that's realistic, since the home would be repossessed if you didn't make the correct payment.

My point is that a standard 30-year loan could, in theory, have any interest rate, but it would still be paid off in 30 years. You just may have a payment that's more than $1000/month.