What you really gotta look at is part quality. You can get higher quality parts from the aftermarket in some cases, though usually not on imports.
Go to GM and get a lower intake gasket and some dexcool for your 30k mile V6, and expect another 30k. Go to the aftermarket and they have improved gaskets and standard coolant which will last longer.
If you keep getting autozone slave cylinders, and they keep failing, try someone else. I have a Z32 slave from o'rielly's and it is working fine now for 8 months (13,000 miles
edit: almost 16k )