^Indeed. I don't recall being realised six months after part 2 did 'Back to the Future Part 3' any harm. Or Kill Bill Vol 2 now that I think about it.
There's a world of difference between a studio pooing out sequels just for the hell of it and releasing multiple instalments in a series. Especially when the films are shot back-to-back and the audience are fully expecting several films before they even see the first one.
The Matrix sequels are a particularly poor example because...well, they were rubbish. Waiting an extra six months to see 'Revolutions' would not have improved matters.