Interesting you brought this up today Joey. Last night was having a discussion with another member about this exact same thing
My grandfather played poker every day. He would walk to the local park - in the nice weather everyone played outside and in the bad weather in the park recreation center. He had one rule - he only played for two hours
total. If he was having a bad run he would leave the table and take a break. If he was having a good run and was way up - 2 hours arrived - he left the table.
Of late, I haven't had the time to play the cash tables. When I did - I followed my grandfathers rule and set a total time limit and I've added a bankroll limit. I asked my grandfather why only two hours - his reply -"I don't want to walk home in the dark"
When I sit I have determined the total time I will play and the amount of my bankroll I will play. If I am working on clearing bonus I may set the time limit as to how many points I want to clear. If I am having a bad run I may take a break or just move to another table. If I lose the funds I allocated to play ---- I leave the table. If I am way up and the total time I allocated to play is up --- I leave the table.