intradaybill, you seriously have to take a class on common sense. If you have a rough 30% chance to be profitable in a given quarter, then your chances of consistent profitability obviously shrink with every new period. I assume that this is something you still understand.
With the numbers given, the sequence of periods is neglected. Why? Because in period 1 it could be Bill earning, in period 2 it's Diana, in period 3 Dave, and in period 4 Henry.
But what is the chance that you, intradaybill, will have a guaranteed profit? After four quarters it's less than 1%. Whereas if we look at the inverse, on average 71% of people lose each quarter. Your chance of a guaranteed loss is therefore a stunning 25.41% (0.71 to the power of 4). Agreeably, the numbers do not consider the sum of money involved. So it could be as Pekelo mentioned, that small losses are made up with a large gain.
Conclusion: The further we look into the future, the lower is the chance of intradaybill being consistently profitable. Statistically seen.