I noticed it all really depends on the girl.
I started doing PE recently and I thing I gained about half a inch in 3-4 months. But when I go at it with my current girlfriend I really have to be careful not to hurt her. When I go in deep I bottom out quite fast and that with only 7.1 inch BPEL.
With my previous gf. No problem at all (although I gained 0.5)
On one side it is nice to know that I don’t have to grow for my current gf. Since I am big enough to hurt her. But I am still going to PE anyway, just because it makes me feel better, and best of all a better EQ!