As you say, re-use is a different issue to ageing - replating is being done because the bolts are old, so it is likely that the nylon has dried too. In any case, the plating on a new part is likely to be superior to that of a re-finished one, and there would be no need to measure the locking torque of the nut to make sure the nylon hasn't failed, only to find that it has and that you wasted the money getting stuff plated......


Chris