Unless the parts I'm replacing come with new (m)
hardware I usually reuse the old stuff if it is in decent condition.
If you are concerned you could put a dab of thread-loc on them.
The only hardware I would replace are ones that are used on rotating assy's in the engine, nuts/bolts for the rods, main bearing caps, etc.
I've had my driveshaft and 1/2 shafts out 2 or 3 times, used the original nuts/bolts, no problems.