If one gets a penny for every second they play, it will take 2^31 seconds or 68 years to reach the horizon and they'll have $21M at that point
(do you offer cash out option? :twisted: )
For counting money though, just use Double - per IEEE it's guaranteed to preserve at least 15 digits during conversion. Which means you can hold amounts up to the US federal budget ($3+ trillion) with precision down to a cent. The nice thing is that even if exceeding that, it will start "failing" in a nice way, i.e. losing the cents like IRS does. Not to mention there is 2 hidden digits precision (it works internally at 17 decimal digit precision equivalent).