newb answer
Good question.
Im a newb so all I can give is my opinion. So here it is.
If it were possible to keep an erection or if you hot wrapped for several hours, my guess would be that it can only do more good. More blood flow promotes faster healing and I cant think of any adverse effects from doing this. It is not rigorous activity on your member so it probably wont break you down much at all.
Stretching , on the other hand, can wear you out after awhile and will probably do more harm than good if you do it for several hours as a newb. Same with any other of the PE that cause stress on your penis.
Feedback plz