Why such timing difference between devices?

[Magicmark]

Hello.  New user here - have found lots of great information already.

I'm interested in a traction device and have read numerous reviews and reports.  Thankfully I don't have much of a curvature issue, but I lost a good inch in length, and was on the short side to begin with.  Would love to get some or all of that inch back.  My disease was acute about ten years ago, so it's been stable a long time.

I understand one popular traction device only requires 30 minutes or so twice a day, while others take hours.  I don't understand why there would be such a difference.  It seems they basically do the same thing:  grab you by the glans and hold the penis in a stretched position. It seems you could increase or decrease tension with any good device, so why would one require such a shorter time commitment.

Lastly, since I don't really have a curvature issue, does that tilt the recommend device one way or another.

Thanks in advance,

Mark