I change rifle barrels when they no longer meet my accuracy expectations. I used to shoot F class and other 1,000 yard matches with at least 1,000 rounds a year per rifle.
Generally, the 6.5x284 barrels would go about 1,500 to 1,800 rounds before they would start throwing more 9 ring shots than 10s or Xs per ten round string, The 9 ring is the 10" -14" ring so when I started shooting less than 95 points in good conditions, I would change barrels.
The 243s would go 2,000 +/- with the same use depending upon the individual loads that each gun liked.
I had a 22.250 AI with three groove 10" twist barrels that shot almost 3K rounds before they wore out.
Generally unless your a regular match shooter, you're not going to wear a barrel.
But, like it was said above, if you overheat a barrel you can gas cut them badly. I once shot out a 243 barrel with one day of jack rabbit shooting in Idaho. We were at the peak of the jack population cycle in the mid 1980s and I ran through 200, hot 58 grain Hornady reloads in about 3 hours.