When we went through the 3-months of the card for my OH, the process went a bit like this:

Day 1: Account opened;
Month 0.5: First statement / bonus paid (actually it came late, but that's another story - it did come eventually);
Month 1.5: Second statement / bonus;
Month 2.5: Third statement / bonus;
Month 3: Fourth bonus, to tie up the full 3-month period.

Mine has been much the same, except that Month 3 is stretching towards Month 3.5 and I'm nervous they've forgotten.