One school of thought is to stay with all stock internals in Glock pistols. Guess that's ok if you buy into the "Glock Perfection" thing.
I have:
G17 - 100% stock. No failures whatsoever
G17T - 100% stock. No failures whatsoever
G19cutaway 100% stock - well.. can't shoot it so...
G20 - 100% stock, No failures whatsoever
G21 - 100% stock, No failures whatsoever
G22 - 100% stock - jammed on the range on me once.. I had worked on it and screwed something up, took the armorers course... figured out what was wrong, and it has been 100% ever since, just like it was right up until that jam.
G23 - 100% stock, actually have not fired this one yet
G26 - 100% stock, no failures whatsoever
G27 - 100% stock, no failures whatsoever
G35 - 100% stock, no failures whatsoever
G37 - 100% stock, actually haven't shot this one either.
All get shot, (except the ones noted) and get shot a good deal, so its not like a box of ammo shot when new, then put away.
All are well into the thousands of rounds. G22 and G27 being at the top of the list.
Perfection, of course not.
Close to perfect as it is gonna get, you bet.