Littlewood was a talented mathematician; pg is an employer of computer programmers. Unless you are doing original research, which, AFAIK, most YC companies aren

Littlewood was a talented mathematician; pg is an employer of computer programmers. Unless you are doing original research, which, AFAIK, most YC companies aren't, I see no reason why you should limit yourself to 4 hours a day. (Apart from having a life, but that's a separate debate.)