As the owner of 3 different trucks with G80's, I would tell you these things:
If it's in a 8.5/8.625, it will blow up eventually.
When will that happen? I really wish I could tell you. Some just die quietly in the night, never to lock again, and others like to go out with a bang. Literally. You may get the elusive 3rd option, where it simply won't die, even with pounding. My G80 in my '00 I sold to my dad had been locked, jumped, put under rapid stress, brakestands, donuts, 35" tires for 45k miles, mudding, hill-climbing, etc.
The G80 in my '00 must have been forged by Jesus, because I've been a member of FSC and GMFS for ~5 years now, and have seen some G80's go with regular driving.
If it's in the 14-bolt (9.5, 10.5), then it will be a lot more robust, but still prone to dying under the right conditions.