IMO, the feeling never truly goes away - you can tuck it away in a box and put it in the darkest corner of your mind, but it is always still *there* kwim? My situation was a little bit different to yours - we didn't have this issue till we were going from 3 to 4 (we had both said all along that 4 would be a great number to have and possibly even 5) and there were times when I felt resolved with not having 4 and I think I really did feel happy with 3 for a little while (and that coincided with DD2 being fully TT and growing up out of the toddler stage completely), but then time went on and DH said that he'd like another, but I wasn't ready and then more time would pass and I would want another and he didn't so it was a lot of too-ing and fro-ing there for a while till we finally decided that this was *it* and the time was right. Have I regretted it? Not on your life. Has the urge gone now? YES LOL. I feel complete now and life is great. I do still get pangs for another one when I hear of someone having another (especially if its their #5) but fat lot of good it would do me cause DH had the snip LOL. So in some respect I don't think the urge/desire ever goes away 100% because afterall we are women and mothers and some of that is hormonally driven too kwim?

Good luck with it all though, I hope you can find peace with it soon (either way you decide to go)