I've pumped for about 30 years and my experience has been that length gains take much longer, and are generally much less than girth gains (in absolute inches). My understanding is that increasing length requires stretching of the "suspensory ligaments" (on some guys that have very little body fat, they appear as two cords just above the base of the penis - like the cables of a suspension bridge. Ligaments do not stretch easily ... I would think that the tensioning devices that grip the penis head and put a long-time constant pull on it with springs would do a better job. Pumping would only stretch these ligaments in shorter sessions. I've added at least 2" to my girth, but only about 3/4" to my length over the years.