Our limit is 4, I figure it can't be much different than 3. With 3 you already are that bigger family, but have an extra seat at the dinner table and extra seat in the car. But 5 is out of the question for us. Even though I would love another I just think it would be too hard to meet all of their needs, etc.
I asked my kids if I should have another baby after this one, and their reply was NO..lol