It would depend on the amount of powder & subsequently the gas pressure, but in any case it appears it would be up into the thousands of shots....I have a couple thousand shots on each of two different rifles and the liners still look like new.
To establish a benchmark, I measured the hole in a new TC liner using a drill bit, and it's .075"....figured I could re-check every year or so and see if the hole is getting any larger, etc...