With pumping alone, I could hardly note any gains. I half suspect the instructions are a bit BSed to keep said gains from happening thus making the product seem a ripoff. I can pump for hours on end, and stay pumped up for 2-3 hours. The trick is keeping it mild.
I haven't felt any problems or pain for something this long, just temporary skin stretch around the head.
However, I as well wonder just how well pumping works with Penis Enlargement. The temporal stretchiness of the penis after a small pump session may be beneficial... to say manual stretches or jelqing.
I'll let yas know what I find out for myself.