It depends on the head gasket, but I would do them anyways. You shouldn't have to replace any gaskets, at most the upper/lower intake gasket. The cork valve cover gaskets can be reused tons of times. Otherwise, it will eat at your mind, soon, causing you to lose sleep at night, breaking out in cold sweats during the day, stressing you out 'til you get an ulcer. I'd just rather retorque the head bolts.