I've maxed out a few blues, and don't quite remember the numbers but they are quite different (a couple only had a few fails, and others failed quite a bit). So if this theory is correct, it needs to be card specific. An easy way to test this would be to reset a blue. Max it out. Reset it and max it out again. If it takes the same amount of cards the first and second time, it is likely your theory is correct. Might take a couple weeks gathering the blue cards though.