This may sound like old story. But, wouldnt
too much pulling the penis put stress on the veins
that come from the testicals upwards into the penis ?
Sometimes it could cause a internal hernia of sorts in
any vein of the penis or any vein coming into the
penis from the testicals. Let me know what the true scientific specifics would be.

Using plastic BANDS to wrap around the base of
the cock, to withhold orgasm, or to use vacuum devices
could be dangerous to the health of the male organ.
Please dont be offended, I would like to know your opinion.

Also, people have to know how to masturbate the
right way or they can injure some ligament supporting
the penis.

At video arcades, they have hard chairs. Now, people
sitting on them and pulling on their penis are
actually pulling on the lower spine as well. They can
get back pain from it.