I am not aware of any independent studies on this practice, so any comments you get here might be just as opinionated as you are seeing elsewhere. There does seem to be some merrit to the ligament stretching idea, in that the penis can be lengthend by long term stretching of the ligaments, but I really can't see how it can increase girth, or even see how grith can be maintained if the penis is lengthened. As you say, there are enough people who do not seem to be affiliated with commercial concerns who swear that it works. Maybe it works for some but not others. If done in moderation, I see no great harm in it myself, and it might indeed help you with stamina, as you will learn to control your erections. That might be the best benefit, but I really don't know how successful you will find it. If you try it and stick with it for a month or more, report back to us.