When should I rebarrel a hunting rifle?

[LR1955]

Clearly, the answer is "whenever I want to". But the question is more like "How fast will it continue to loose accuracy?" When new, the Walther barrel shot like .25 inches; and now its up to like .8 inches.
.8 inches is good for now, but when it gets up to 1.25 inches @100 yards I will want a new barrel. Is there a formula that will tell me when that will be?

Drift:

I would imagine you need a new barrel for a Grendel after about 8K rounds fired.

I would really be skeptical about accuracy loss with a gas gun by shooting groups at 100 yards. I would be more convinced at 300 yards.

No need to buy a new barrel unless you need one.

LR1955