When you’re considering barrel life, you have to define your expectations from the barrel. Any AR barrel will go bang and send rounds down range for - effectively - an unlimited round count, but that doesn’t mean you can do anything with the rifle with that many rounds down it.
I have a Bushmaster Hbar with about 15,000 rounds on its second barrel, and went over 20,000 with the first barrel. It still goes bang, and for simulated door-kicking, it works well enough - but it’s not winning any precision competitions.
Alternatively, I expect 3,000-5,000 rounds of usable barrel life from a Service Rifle barrel - 3k for button rifled barrels, 5k for cut rifled barrels. By 3-5k, the barrels aren’t going to hold 1moa any longer and I’m going to drop points, drop points just for being too cheap to replace the barrel.
The 223/5.56 is pretty barrel friendly. Comparatively, I have an LFAR in 6 creedmoor built for precision rifle competition, which is only going to make it about 1200-1500 rounds before it tanks. I’ve only made it 1200 rounds with my last two bolt gun barrels in 6 creed. Beside it, I have a 243LBC (6mm Grendel) precision gas gun which will only make maybe 3000 rounds. I shot a 243AI for 600 & 1000 yard Benchrest for a while, which would only last about 700-800 rounds before it couldn’t be used. Any of these would still deliver “huntable groups,” but were a long way from competitive any longer. Either accuracy slipped, or velocity was falling off fast enough that the long range trajectory was no longer reliable. My 6 creed match rifle last season was losing ~35fps per 100 rounds at the end - which meant in a 2 day PRS match, my bullet would drop 14” more at 1,000 yards on the second day than it did on the first. Not acceptable.
So again, it all depends what you ask of the rifle. If 2-4moa is your tolerable standard, and you’re not shooting far enough for varying bullet drop to matter, an AR barrel will last forever. If you’re expecting itty bitty groups, and shooting long range, then you’ll need to plan on a new barrel every year or so.