We had all of the same reasons as you listed to not have another baby. Our next youngest was five and a half when we had our baby. We don't regret it for one second. It is very different starting over, though. There are a lot of things we forgot about. I think he has a calmer, less easily ruffled mommy than the others had. If you have felt this way for years I would guess that probably will not fade and you'll regret not having another baby. I say go for it!