Instead of practicing all the time, go and listen to an opera or read through a symphony, and you will find it will improve your piano playing much more.
S. Richter admitted in his published notebook that he had practiced 12-14 hours a day (if my memory is correct).
Can you really concentrate for that length of time?
I heard from a pianist a couple of days ago after a performance that all the best never practiced more than two hours a day. I find this hard to believe, if someone is to classify Horowitz, Cziffra, Rubinstein, etc. as the best.