from the looks of it, not many play electric drums here?

how do you guys sustain stamina for your kick drums? i'm only able to sustain for half an hour and then i'll start playing off beat. one of my pro friend places his whole feet down and raises only the front part of his feet, while i tend to have my whole feet up. his technique sustains stamina, but with his technique i find playing faster beats difficult.

what should i do to improve my kick drums? should i focus more on the technique, or should i just exercise the whole leg more?