I could only hope to live long enough to wear out a 444 barrel! It's low pressure enough and has a large enough bore expansion ratio to let you shoot thousands of rounds without worry. You are much more likely to wear out the bore by over cleaning it. JMHO. DP
By wear out what do you mean? If you mean shoot till it's not accurate anymore I would say at minimum it will be in excess if 10,000 rounds. Maybe closer to 20,000. That would be till it goes from say 2.5MOA to 4MOA. Of course a single good nick in the crown can do it tomorrow. It's a gun that will last several lifetimes.
Good luck on that one.. they are pretty much 'Bullet Proof'....
For 'plinking' in the 444, I load 'er up with 17gr of Trail Boss and 180gr XTP's.. The wife just loves chasing those little Orange bouncey targets around.
In the 45-70 I do 17gr TB and 300gr HP's.
Don't see any barrels wearing out, 100's of rounds.