I haven't read the whole thread. I have four (18 in two weeks, 7, 5 & 20 months). I've always wanted four, and I'm glad I have them, but in some ways, I should have stopped at three. But, the reasons have very little to do with the number of kids. DS2 is more work than the other three combined. I'm older than I expected to be when I had my last (had her almost two weeks after my 41st birthday). My journey to get here involved traumatic birth (unwanted c-sections), secondary infertility, multiple miscarriages and a stillbirth. Between the PTSD, depression, physical havoc of the surgeries, etc. I'm pretty wrecked. If ds2 weren't so high needs, and if I hadn't fallen apart over the course of the last few years, I think things would look a lot different.
And, honestly - as wiped as I am, and as hard as it is (I get out of bed every morning, even after a full night's sleep, feeling as though I got no rest), I wouldn't trade it for the world. We had photos of the kids done last year, when dd2 was about six months old. Every time I look at those pics of the four of them, I feel my whole body fill up with the knowledge that this is exactly the family I was meant to have, and I wouldn't trade it for the world.