Moonrunner - I was a Fed - We qualified four times a year - 60 rounds each time - plus we were given a box of 50 as practice ammo. Those who shoot more are SWAT type teams, and even then the average agent does not fire near 25,000 rounds. 25,000 rounds would be fired by those testing an arm proposed for adoption by his service.
Most firearms will not last even 10,000 rounds before they become too worn for practical use and become dangerous.
I don't think you can categorically state a number like that. It depends on the gun, make/model, ammo used, etc. http://www.thehighroad.org/archive/index.php/t-434260.html