It really depends on how long you are prepared to stay with it. I have been practicing PE for a little more than 4 years now and have gained about 1.2” in length and ~0.5” in girth. Most of my gains came the first year though.
"You are entitled to your own opinion, but not your own facts."
buby
I think that once you get to know you can gain some, you can can gain any amount.