of course, making your rotors or drums thinner when you dont have to is not necessarily desireable either. GM now advises against it unless absolutely necessary.

and replacing good bearings when replacing said thin rotor with a new one which comes with new races is an unecessary expense IMO.

papa always said "dont fix what aint broke"

those two never could agree.

had ta mention machining rotors... didnt ya?.
GMs new policy (circa ~1990) is kinda weird. DO NOT machine rotor unless grooves exceed .060", or thickness variation or runout is not within tolerence.
if the groove is that deep, the rotor is below spec. if you have a thickness variation, it's gonna come back about half the time, unless you just replace the rotor, in my experience.
then they say if you do turn it, it's on-car only.
block sanding is permitted.
this aint word for word. i dont wanna find the TSB, but you can if you want to. i'm sure it's more applicable to the new cars than the old ones, but i consider a variation of it a good policy for all cars, and it has significantly reduced my comeback complaints to almost zero, and MTBF is down.