Len pretty well nailed the answer. A pre approval is ok for submitting with an offer on a home but, they will go back to the underwriters for final approval and committment when you go under contract anyway. Like Len we all have lenders we deal with on a regular basis. I have four different lenders I refer clients to depending on their situation.
Hope this helps,
Being pre-approved can mean many things, depending on who you speak with. For example, although I do not work for a lender, I can "Pre-Approve" you for a home. Typically, pre-approval does not have a time frame. It simply means that a cursory look has been made to see if on the surface you could qualify for a mortgage. It also DOES NOT mean that you positively can qualify. MOST pre-approvals are based on unverified income, credit, debt ratios, etc... Please verify with your lender where you stand. If you have not yet submitted a formal application and do not have a mortgage professional in mind that you would like to use, I would be happy to direct you to a few reputable people with years of experience who would be happy to help you. If you choose to find someone on your own, be careful who you choose. Like a real estate agent, the wrong mortgage person can be an anchor around your neck when trying to buy a home!