Usually the maximum profit depends on the house's bankroll. Depending on the house edge, it's often around 1%. So if the house owned 10 Bitcoin, the maximum profit should be 0.1 Bitcoin. With dice, it's easy to set a maximum bet size, but with 500xBit, there's no hard limit to the amount you can win. You should probably set a certain "auto cash out" around 1% of the house edge on top of a certain maximum bet. This protects you from going bankrupt