As the questions says, when do you stop? your point of no return?
a. at least double your money, then stop
b. you only stop when you have lost all your bankroll money and then blame the casino?
c. or you are a superstitions gambler, when you have signs like losing 3 straight in a row, then you quit because you know that you're having a bad luck
d. you stop when you are at least break even
I didn't include chasing your losses as obviously you might to continue.
None of the above.
My strategy is different from all your options available on your topic, there is no time that I can't put an end to my gambling activities, when I will stop depends on what the casino have in mind for me on that day.
Yes I started gambling with the mind of getting some fun out of it but if suddenly or as soon as I started gambling I get lucky, that's the end of the fun for that day, I will be coming back the next.
A sudden win is a sudden luck, it won't stay for long and believe me if you keep gambling you can lose everything and never see such day again until a very long time, I quit once I win and if I don't win I keep having until I reach my threshold for the day.