Wheel rims live a very long time, but are still consumables when used with rim brakes.
If they're not damaged, braking will wear out a rim in 20,000km ~ 100,000km in my estimates.
The back wheel wear is accelerated by being dirtier, so the rim has more abrasive grit on it which is collected by the brake pad and pressed into the rim, acting as a grinding dust.
The front wheel's wear comes from doing 90% of the braking effort.
You can extend your rim's life by
Inspecting the pads every 1~3 months, and using a pick to extract any embedded debris in the rubber. You'll be surprised how many flakes/shards of metal are in there, and they're all scoring your rim at braking time.
Wiping the rim clean periodically. If you rub a clean finger on the rim and see a dirty mark on your skin, then a quick wipe around with an old rag will improve your braking. Do both sides, and remember the sector of wheel that is under the caliper/stays too.
This is more important in winter when the roads are just dirtier.
Avoid riding through deep puddles where you can, and store your bike in the dry After a severely wet ride, give the rims a wipe down.
These tips will help you extend your rim-brake rim's life.
High load does not wear out a rim, but it may increase the chance of going out of true or splaying the sidewalls.
I have hit a pothole hard which popped a rim weld on the rear. I forced it back into line, but the result was a tiny step for the brake pad to go down, which ate a brake pad in a couple months.
Steel rims last much longer than aluminium, but noone really uses them for weight reasons, and aluminium rims have far superior braking performance in the wet.
I can't speak for carbon fibre rims, have never owned one.