We had our three within 4 years. Benjamin was barely 4 and we also had Amelia, who was 21 months old, and a newborn. There was already noise, mess and no sleep, so we figured another baby wouldn't make any difference LOL
I eased Rachael into the family's routines. She was never a good sleeper, and that was hard, because I was always really tired. And then dealing with a toddler and preschooler also was very tiring.
But, I am glad we spaced them like we did. And I am glad we had the third one, Rae has added so much entertainment to our lives...LOL. I really want one more, but with Rae over 4 now, I can't really go back to babyhood, I think the spacing would be too much. Right now, my kids are 8,6, and 4, and I can't imagine going back. But I long for it, I really do, and wish I had made the decision to do it a year or so ago.