Thank you for correcting him in a constructive manner before I sounded like an asshole.
The reason you see a lot of people buying axles from auto zone (or any other auto parts chain) is because they buy axles from auto zone. No, the axles aren't indestructible, just like any car, they will break at some point, and you can't expect to replace them with (poorly) rebuilt stock (if that) axles and have them last any amount of time. It comes back to the fact that people are cheap at modifying these cars and an axle from you cost <$100 instead of the $200ish it would cost to get one from Raxles that's stronger and will last.
Having said that and coming back to the point of it being n/a, I don't see why he would have any issues, other than the normal wear and tear, with his axles.