playing with profit of course is a good strategy and safe. I always do this to keep my bankroll. so that I don't lose it all in an instant.
I agree, using your profit as a bankroll is really a good strategy in gambling. You have nothing to lose from it but only your time that you put to earn that profit. It still a better strategy than accumulating your profit and gamble it together with your bankroll. No one knows you might lose the next time to bet. So it is better to be safe than sorry.