I think rad wise, the main things that can go wrong is dust (which can be cleaned), clogs from coolant reactions or algae (which can be cleaned) and leaks (which can be avoided by not shoving a screwdriver through it).
Lifespan of rads are pretty long i would think. Have seen some watercooling builds which to this day use radiators from before PC watercooling equipment was mainstream and these rads are apparently still going strong!
Maybe if you treat your rads right, they will even outlast the case!