A pre-approval letter is typically good for about 90 days. After that, it is considered “old”. If you are overseas earning foreign income, there are some restrictions on whether or not you can borrow as well. You need to discuss these things with a lender.ost preapprovals are good until you put in an offer and then once you move forward with the loan, the commitment will have a drop dead date on it–usually 60 days but sometimes 45. It is a good question to ask when you apply.