Well, let me put it this way: Aside from tearing your dick off, your body is going to heal those little micro-tears regardless. Ones goal through hanging is to manipulate that healing process, not prevent it. If you simply reached fatigue (creating those little tears) then took a break, allowing your body to completely heal, that area will become stronger, in order to prevent further damage, and the end result will be a tougher but not necessarily a longer dick.
This doesn’t answer what mgus asked. I.e., if you are not going to let your penis healing, the microtears will accumulate; at the end an injury will come.
Hard work requires recovering days: just so simple. What Manzwa posted make more sense, but: how you can be sure to not go above the overstress line (a thin line, as he explained).
A light tension, using an ADS or an extender, could allow the body to heal at the same time that microtears are verifying; it could also avoid that the penis will return to it’s original length. But hanging day after day for months, with no rests, appear to be dangerous.
I would add that is generally not considered that hanging cause a stress not only on your penis, but on others bodyparts: first of them, back; hanging 2+ hours a day with (for saying) 10 lbs is more stressfull than deadlifting 500 lbs for a total of 60 seconds 1 time per week, as any orthopedic Doc would confirm. Your back is at least important as your penis, and won’t heal so easily.