A pre-approval is typically good for 90 to 120 days, depending on the lender. That is the window in which your credit report is still considered current. After that, your credit may need to be pulled again.
I have hands-on relationship with my clients. I stay in communication with you, and I will check in with you throughout the period of time that you are looking for a property. If you tell me your data hasn’t changed, and you can provide updated documentation supporting reported income and assets, I will keep issuing a pre-approval letter until you get into contract. We may need to re-run your credit after the 90 days has expired, but not always.