I once went in excess of 3,000 rounds on my issued 3rd Gen G19 without cleaning or lube - just to see what it would take to choke it up. My team sergeant finally broke down and cleaned it while I was out of the office before we went on an extended deployment - he's probably a lot smarter than I am!
On my personal duty guns (9mm Glocks, Gen4, all of them), I guess they get detail stripped and thoroughly cleaned once a quarter. Now, with my limited range availability, that probably equates to every 1,000 rounds or less. RSAs get changed every year - otherwise I just keep on keeping on with them.
If I was shooting a high end 1911 with very tight tolerances, I'd probably clean after every range session out of an excess of caution.