you profit should be to around 10% a year.
Did you throw a dice to get that number?
There are a lot of factors influencing
expected profit, and it's different for every site you invest into.
You can't say any number should be the profit, and you can certainly not say a universal number fitting for all sites.
No i have invested in bankroll in one casino now for leik 15 months. Longer period of time you have invested more closer to steady income you will get. If you have investment there for only a month is a gamble.
Biggest part is that your founds are secure. Since if site gets hacked or scammed you will need 10 years to recover.