Your answer of 4 is purely based on mathematical logic sadly if you ever had bred ball pythons you would know that breeding is hardly about math and is hardly textbook.
Yes we all know the mathematical possible outcomes of a clutch, however when breeding there is such a thing as missing odds and sometimes the opposite is true too.
To the OP
Depending on the number of eggs in each of your clutches I would give it 2 to 3 seasons.