Answer: -No, you're thinking of the universal default rule with credit cards where your APR can go higher if you miss a payment on the aforementioned credit card or any other credit cards. But credit card payments are usually always variable.With a mortgage, regardless of your credit score, your interest rate will remain fixed for 30 years if you're in a 30yr fixed mortgage. The only downside is if you need to refinance down the line, or if you buy a new home. By the way, you've got a great rate. -No. Not unless you have something strange in your loan papers that allows this, but I've never heard of such a thing. You rate is fixed for the life of the loan. -If your loan is truly afixed loan, the interest on it can not change. If you decide to refinance however, your interest rate will be reshaped against your credit at that time. In southern California, a 30 yr at 5.4 is a good situation. I wouldn't change that unless you absolutely have to. -A 30 year fixed mortgage will maintain the same interest rate you started at for the life of the loan (the full 30 years) no matter how your credit score changes. By the way, in case you didn't know, you have a great interest rate for a 30 year fixed in California. Currently the interest rate for a 30 year fixed, no points is 6.250%.