I have been doing 300 push-ups and 300 squats almost every day for the past several years, just because I am cheap and the thought of paying for a gym membership runs contrary to my beliefs. But my workout is in sets of 10, alternating between a set of push-ups immediately followed by a set of squats, then 15 seconds of rest until the next set. Even with little break between my sets like I do now, I don't think I could do 100 consecutive push-ups, and even if I did, does it really add to fitness? First, I think I'd be exhausted and would not have the energy to do more afterwards. Then, I think it is much better for overall fitness to spread the workout over a period of at least 30 minutes. No science to back me up, only my impression.