There are videos of a Para 1911, shot by Todd Jarrett, as fast as he could, for 1000 rounds without stopping to clean or lube. The gun got so hot he could hardly hold it and there was not one failure of any kind.
The point is, of mainstream, full/mid size guns comparable to G19s and G17s, all should easily be able to run 1000-1500 rounds without cleaning.
But the thread is not about how many rounds a Glock can run without cleaning, it's about what experiences gen 4 owners have had especially with regard to brass to the face.
It seems if a gen 4 is gonna have the problem, it occurs around the 1000-2000 round count.