How do you know you are done having kids?
You give away your maternity clothes.
You get serious about losing weight again.
You give your second-born a middle name that was the runner-up for the first name. No hanging onto it for a third.
You buy a family car that comfortably seats your family, as is.
Then you name the new car one of the names on your girl short list. No use for that anymore. Might as well get to enjoy it on something in this family.
You start a small business.
You even buy a house that fits you all, just.
If you are my analytical husband you go completely crazy and take the "C3" (child three) column entirely off the master budget spreadsheet.
And then you take a pregnancy test and find out that you are not, in fact, done having kids after all.
Bring it on, sweet, surprising, wonderful, overwhelming life. Everybody here is up for the adventure.