Increase Botox for Better Result?

I've been having Botox injections around my eyes and a little in my forehead for several years. Generally, I find the results to be unimpressive. Does having a larger quantity of Botox in one session make a difference to the results? If you have more injections,say twice or three times as many in the trouble areas, will it give better results? Due to having injections in my central brow area is it possible that this has caused a lot of new lines?