I have gone 1000+ rounds with my SP-101 and my old Security Six.
They are both 357 mag caliber and I shoot mostly moderate 38 Special loads with occasional cylinder full of 357Mag barn burner loads. I load good quality/correct sized hard cast bullets so bore leading is not a problem.
The service interval is much more dependant on the quality and size of the bullet along with proper relieving of the forcing cone and cylinder throats. Generally if you keep the bullets under 1000 FPS you are better off.
I have one GP that hates lead bullets, it doesn't shoot them as well as jacketed and it leads horribly after just 25 shots, the other goes 2-300 in a steel match with no problems and barely has any fouling even then.
Have shot 400 rounds of 148 gr. BBWC's behind 3 grs of BE through my KGP-161. It was a very accurate load and didn't show signs of tight extraction after all that. Just cleaned it because.
My KGP-141 showed signs of difficult chambering in a couple of chambers after 200 rounds of the same loads. My theory is that I shot the gun a few times with less than a full cylinder and that may have fouled the empty chambers.
Now I've changed my load to 158 gr LSWC behind 4.5 gr of BE. Shot 150 rounds each through my 4" and 3" GP today and so far function has been fine with easy extraction and loading.
Will try to see how far the gun will go without cleaning.
I'm considering getting the chambers reamed to .358 eventually but will have to see how my GP's behave with lead bullets in stock form.
My Bisley Vaquero, using black powder will go 75 rounds before tying up the cylinder. Using smokeless, it'll go at least 500 rounds (I've not run it longer than that without cleaning).
My other single action and double action revolvers will run hundreds of rounds without cleaning. My 1911's will run several hundred without cleaning also.
I generally just wipe them off between sessions and put off cleaning until I have 500 or so rounds through them.
I NEVER have any leading problem with any of my handguns. It might happen when I first get them (had a problem with a new SS Bisley Convertible .45 until I reamed the cylinders - then it all went away).