I am not really in the same position as we only have 4 children. Although I don't do pregnancy well and have had 3 complex births out of the 4. I could still have another 1 or 2 if I could get pregnant and DH felt the same way. I could nag DH and probably get my own way but what is stopping me and why I agree 4 is plenty is
1) we absolutely can not afford it without everyone making huge sacrifices (and the older kids don't get a choice but would miss out on a lot) and
2) DH has helped me achieve my dreams with my career, home, family etc so I feel its my time to help him achieve one of his which requires me to work a lot more then I have the last year and be in the position to contribute significantly to an investment loan.

Before I had my last baby a month ago I couldn't have reached that point and wanted another right or wrong. The decision now is much easier although its a little sad that all his firsts are now my lasts if that makes sense.