1 - (1 - .025^2)^1339 =~57%
Using exponents 3 and 1338, you have about a 2% chance of hitting a triple on any given day.
Now we're on the same page. Though, I don't think it's correct to subtract from the exponent like that, but I could be wrong.
Consider a group of three consecutive blocks.
Your chance of winning at least one is
1 - (1 - .025^1)^3
Your chance of winning at least two in a row is
1 - (1 - .025^2)^2
Your chance of winning all three is .025^3, or 1 - (1 - .025^3)^1.
The sum of the exponents is constant.