Constant PE theory
Here’s the theory.
When you start your penis is hopefully not used to stress, and minimal amounts can make you grow.
If you are continually gaining you keep the tissue in a weakened state, by preventing full healing. This makes further gains easier.
If you stop for a while, the penis has a chance to heal fully and strengthen to resist the forces, to which it is now used.
So the upshot is starting with the minimal amount of force required to gain, and slowly ramping it up only as gains slow but never stopping to allow full healing is a way to guarantee best growth with the minimum amount of force and time spent.
Even using this method the penis is likely to gain strength, and techniques like modifying the routine from very length based to very girth based, to mix it up a bit, may be needed to continue gaining while sticking to reasonable levels of stress (ie those unlikely to cause injury).