How often should I clean my ruger sr9 semiautomatic?

I've been cleaning the bore after each trip to the range (50-150 rounds), but it's not usually very dirty. I've heard of testers firing thousands of rounds without cleaning it at all. I've fired probably a thousand or so and never had any problems. I just purchased it about a month ago and hadn't owned a gun in 20 years. Shot revolvers when I did have a gun.