The bullet weight, barrel material, and the method of rifling will all have an effect on barrel life.
If you shoot 55 grain bullets, you will enjoy a very short barrel life. If you shoot 100 grain bullets, your barrel life will probably be longer by a factor of about 10 times.
I have several hundred of the .243 uppers in the field, spread out over about 3 years and have yet to have my first barrel come back being "shot out"