Nothing is permanent, PE or not. As we age, we tend to get smaller, weaker, more frail, etc. If you don’t have some kind of regular exercise regime for your penis, it will get smaller even if you never PE’d. Look at the members on this forum who started PE after…remembering how large they were in their 20’s, then measured in their 30’s or 40’s to disappointingly find that they had lost size, then quickly regained it with PE and then some.
It makes NO sense to put forth as much effort as PE takes, and then just stop completely without even a bit of maintenance. We have members here who are watching their penis dwindle away just to post about it, after it literally consumed their lives for years. Make it fit in with your life, not overtake it, and then you can continue until you are dead. Good luck!