cylinder head bolts re-torque

[ANVIL99]

Hello guys, last night I finally got to re-torquing my cylinder head nuts on my 92 fj1200abs(trying to stem what I believe is a base gasket oil leak) and boy where they out of
spec.Most of the 12 nuts began to turn just after 15 foot lbs (cold engine) of torque so I tightened as per my clymer manual torque sequence.Bike has 77,000 km on it.Is this
something that should be done as part as maintenance on a older bike and what are the pro,s and con,s to doing this? note: I did not loosen the nuts first and torque is to
be 25 foot lbs.