Exhaustion ? No, I have never felt tired to that degree. I sometimes feel somewhat spent after a continuous hour of improvisation and recording but it is a pleasant, happy sort of tiredness with a sense of achievement, and nothing a good rest will not dispel. Provided you are otherwise healthy, getting enough rest, food and exercise and are generally happy, I cannot see why playing the piano should exhaust you. Perhaps it is a mental issue; perhaps you are not enjoying yourself at the keyboard any more. Then again, what do I know ? I do nothing that could properly be called practice.
You should feel mentally exhausted not physically.