I begun PE in january 2018, got 5mm gains in BPEL.
My advice :
It’s not just about your PE sessions, but what you do before and after it too.
For example : heating isn’t enough in my opinion, I try throughout the day to keep my unit the most relaxed/extended possible, by stretching it everytime it starts to turtle/retract.
Also, jelqing is a must-have (or a must-do in this case) , it will help you recover faster from each stretch session, just learn to do it, go slow, put a lot of lubricant, watch videos about it, study.
Don’t focus on the numbers of your routine, focus on the feelings you get.
For example , when I stretch, I don’t start counting until I feel that my whole unit is being stretched, you got to feel tension in it.
Finally, try some differents exercices, like V-stretches and other ‘fancy’ stretches, search for the “stretching” feeling each time you PE.
START: BPEL 13.5cm ////// NOW (08/02/2018): BPEL 15cm.
Beginner goal : BPEL 15.5cm
I call millimeters "soon-to-be inches".