The resolution of the graphic is only in years. I don't think there's a sudden drop, I'm fairly sure if I were to resolve this to months, it would be a fairly level decline.
And quite frankly, 2 years is pretty good. How many AAA games have you played for 2 years? I'm pretty sure I can count them on one hand.
Two years is indeed pretty good, you're right: but BM is a game that can so obviously keep people for longer. And it might still be level across that period, but it won't be level across the whole period, though maybe it's a kind of bell curve.
