I've always wanted 3, and am pregnant with my 3rd, and I definitely feel 'done' already lol!
#1 and #2 I felt overwhelming cluckiness with, nothing would get in my way!
I always have had it in my head that I wanted 3, so this one was just a matter of following through with the plan. I had 2 embryos left, and if neither worked, then so be it. Luckily, the last one did and here we are - my plan is coming along nicely, and I'm sure the urge to procreate will be gone I hope.....