With the big ones only {over .400}:
HEAPS - 100 - 200+ easily.
Partly dependant on how many DR's I buy
as all get 20 - 40 shots through them while
working up a load that works in them.

How many shots do you fire per range session?
20 per gun Max

How many shots do you fire per year per rifle
{caliber/rifle stated}?

Depends on what I am doing each year and which
doubles I take out with hunting with me.

I try to take a different DR hunting each year.

If I take a DR hunting / culling, I'll take
60 rounds (about 5kgs which is the limit to fly with)
and apart from 2 to check the regulation most would
be used before I come home.

Edited
Max I have is 500Nitro, 505 Gibbs and 500 Jeffrey.

If I have a 600 or 700 Nitro,
I doubt it would be 20 shots !!!