I look at barrel life in 2 categories.
Category #1
A rifle that I "normally" use from 100 to 400 meters.
If it gets 1" to 1 1/2" MOA, then it's good to go.
Category #2
I like my 1000 meters units to be "able to pull off 1/4" MOA.
If I shoot 3 groups of 10 shots each and 65% of the bullets "on average" are out side of the inner ring,,, then the rifle gets a new barrel.
This is done at 900 meters / 1000 yards and "hoping" to land the 65% of 30 shots in-side the 5" ring.
That is a 10" V ring for the TR folks.
The above is a rule of thumb, so pick and choose what works for you .
PS: It is wise to do the rifling barrle test on the calm-est of calm days to lesson the chances of this becoming a factor .
No wind and the best of shooting skills are priority 2,,, the steadest of "hand & eye" will determine priority 1.
Only the shooter will know when the time is due.
Western Canada Don