I think the point is being missed.
The question is it permanent and the answer is yes, however sure you can lose 'gains' but those 'gains' will not have been what is dubbed cemented and become permanent, otherwise you would never have lost them. Once the penis has grown and that growth has become permanent it will not lose those gains, and the only time it would seem size has gone down is when we get older and less circulation down below or health reasons such as heart or maybe medications.
It often takes months for gains to become permanent. I have taken several year breaks from penis enlargement, comeback and I ain't lost anything. Stillwantmore is another guy who knows this is true, having also taken extended breaks and lost nada.
If you gain in lets say 2 months and stop it altogether, then yes you will most likely lose it but that isn't permanent results you had.