You sound like a benchrest shooter

They throw the barrel out when it starts shooting worse than 1/4 MOA.
What calibre mate? Even my hot as hell .25/06 rounds still group pretty well after 2,500 rounds. My .22/250 40° Ackley still shoots 1/2 MOA after 1200 odd rounds. I've heard of benchrest shooters binning 6.5mm/.284 barrels after 1000 rounds but that's a pretty overbore cartridge and if they can't win a world title with it they chuck it away. Some of the big belted magnums are bloody hard on barrels. There is actually a barrel life calculator on one of the websites that is very interesting. It's apparently quite accurate too and relatively well proven. If you tick the "moly coated" box your barrel life goes up substantially and if it is true then it is well worth the extra expense of running moly coated projectiles.
There is also minute of angle and then there is minute of animal
Heard a classic tale the other week out the SARA range where one of the older guys is actually a full time pro shooter - great guy, has been around a long time, and is really interesting to talk to. He was up in the Flinders Ranges doing a goat cull a few years ago and a heap of floggers from Adelaide went up too. One of them was a very high profile benchrest shooter. Anyway this pro shooter reckons he was an absolute joke as he was gut shooting goats because he couldn't shoot for sh*t without resting on a bench then bouncing rounds off the rocks everywhere as he tried to finish them off. Most people would have assumed this guy could shoot the balls off a fly at 200m after reading some of his articles in some prominent gun magazines but alas. The guy at the gun range heard this bloke was coming and was really looking forward to shooting with him. Turns out that off a range he was useless.