The longest period for which the lender will lock the rate and points on any program.
On most programs, the longest lock period is 90 days; some go to 120 days and a few to 180 days.
It is extremely important that the lock period selected be long enough to cover your home purchase closing. On a refinance, the period must be long enough for the loan to be processed. This can vary widely, depending on the lender's workload. Discuss the time required with the broker or lender.