Tracks lifetime

I want to know what your experiences are about the expected lifetime of the undercarriage tracks lifetime.

I have a CAT 320DL and got it with ±4000hrs.
Now at 8000hrs, have I replaced the chains.
How much traveling is too much for an excavator per shift/day/month?

I am making money through rental to a client.
The machine travel quite a bit per shift.
I am concerned about the traveling and want to discuss this with my client.

I am safe to say 8000hrs on CAT320 tracks?

Tracks lifetime