Mortgage rates are volatile, so the decision to lock your rate is a bit of a gamble. Lock in too early, and you might miss the opportunity for a better rate. Rate locks often last from 30 days to 60 days, though they sometimes last 120 days. Some lenders offer a free rate lock for a specified period.A longer rate lock tends to be more expensive. For example, a borrower who chooses a 30-day lock on a fixed-rate 30-year loan might pay a 4 percent rate and zero points, while a 60-day lock might cost 1 point (equal to 1 percent of the loan) or a slightly higher rate with a half-point.Learn more: Guide to mortgage rate locks