It depends upon the cartridge. For competition rifles like @Big Uncle and I are talking about, “death comes on swift wings.” Break in - meaning where velocity seems to stabilize and the rifle seems to find itself - is typically around 100-200rnds. Then for these competition rounds, groups might start to open at 800, velocity start slipping at 1000-1200. A Benchrester has to give up on a barrel at that first mark. A Precision Rifle Competitor can hang on a bit longer, waiting for the velocity to fall. We can win matches with a 3/4-1moa rifle - we just need every round to fly at the same speed.

The barrel on my main match rifle last season was a Rock Creek tube, the beginning of the end started around 500 rounds. It was losing ~15fps per 100rnds by 1000rnds. I was stuck with it to finish the competition season, which took me through 1470 rounds. I spun it off at 1471 rounds - which was at least 600 rounds too late. It held onto enough accuracy to compete in PRS, but the velocity was a terrible downhill slide. I ended the season shooting a high node load, 1.5grns higher than where I started the season, and was still something like 200fps slower!

The replacement barrel this season is at 794 rounds currently, and holding onto the exact same speed for the last 3 work-ups. I have about 700 rounds left on the match schedule for this season, then it’ll come off and get replaced for next season. The only reason I made it through the season on one tube is the fact I lost 2 months of season due to work schedule, and missed several matches. I HAD planned to change barrels between 4th of July and now, but I missed enough matches early on to make this barrel last all season. I also did my practice with other rifles to save my match rifle.

It’s all about the accuracy demand/expectation for the application, and the overbore ratio of your cartridge. Like @Big Uncle mentioned, my first 6.5-284 barrel for 600/1000yrd benchrest was toast after 800 rounds. I shot a 243AI for a while which was already done by 700. Alternatively, I used to expect 3500-4000rnds from a Service Rifle barrel. For PRS, we don’t have to shoot quite as small as benchresters, we just need consistent velocity and ~3/4moa. Rounds like 6x47L and 6 creed should make it 1200-1500rnds before failing to make the grade for PRS, but they’d be toast long before that for benchrest. We expect a bit more from the 6BR based cartridges. Guys running 6.5 Creed might get 2500-3000.

We also have to consider the logistics of replacement. I have/had 3 matches in 3 weekends this month, then leave for a hunting trip next week, then 3 matches in 6wks to finish out my season. I don’t have time to have my rifle out at a smith for a month, then spend another week or two in load development right now - I need my barrel to hang on and make it through the State and Regional Finales. But even if it DOES make it through the end of the season, I’m going to change the barrel this winter, so I start next season with a fresh tube. I’ll shoot two rifles next season so I know I will make it through an even heavier match schedule next year, and rebarrel both at the end.

The good news - or maybe just the “reality,” since it’s not really good news - is the fact the barrel really isn’t so expensive in the scheme of things. I generally figure $250-350 for Regional level PRS/NRL matches, and $800-1000 per National level PRS/NRL match. Lower level guys like me might shoot one or two Regional matches per month during season, and 2 or 3 National level matches - good for about 6-7 small matches and 2-3 big ones. That’s 1400-1800 rounds - easily finishing out a barrel in one season, good for about $700 in replacement cost. BUT - spending over $3,000 in match fees, hotel, reloaded ammo, fuel, and food on the road. So the barrel cost isn’t really terribly consequential.