My piano stands in my room. I see him (his name is Wolf) everyday. To keep him handsome, I dust him clean every morning.
But I don't play everyday, at most 5 days a week. Some days of rests allow my tired hands to recover from any strain caused by working at the computer.
I usually do 1 to 2 hours during a session, since I am not at home in the day. During those sessions, I am most motivated when learning a new piece. I can hardly pry myself away from the piano when I am in the mood to improve a piece

Sometimes I can go without a sip of water for hours when I am working at the piano, because I can't bear to leave my stool.
But when I play too much of a piece (especially an exam piece), mental fatigue sets in, and I have to take water breaks during a session to refresh myself. If I have had enough of a piece and seem to have hit a bottleneck, I would put it aside for a day or two, so that I don't risk hating it.
I just go with my heart, and a little practice notebook to keep track of progress. Sometimes long practice sessions work. Sometimes they don't, and switching to mini practise sessions work better for the time being.
Theoretically, I can play throughout the night if I want, since I have a digital piano in the living room. But to sit up in the living room in the middle of the night might worry my familly members, so I hardly do it. If both pianos were in my room, I might be making music throughout the night...