We are on the 3 year plan. :-) After our latest birthday this year we will have a 9 yr, 6 yr, 3yr, and approx 3 month old...
It works for us. But its really what works for YOU. Our older 2 are in school, I have alone time with our almost 3 yr old, and he will beable to play with baby for almost 2 years (aka bonding)...
The older 2 are old enough to help out around the house and help occupy the younger one when baby does come.
Some say that the more you have is more expensive. lol Only if you get rid of everything you had from the other kids... I have totes in the basement of clothes that cover all ages and sizes. Plus all the gear. I nurse the babys for the first year. So for us the only EXPENSE is diapers... Since we have the kids approx around potty training time of the next oldest there is very little over lap of having 2 kids in diapers.
Relax and don't worry... Its not like you pee on a stick and violia the baby is laying there... You have 9 months to prepare... And we all freak out a bit when that test comes back positive... Its the What IFS...
My older sister and I are 1 yr 9 mo. apart (we fought like cats and dogs growing up)... My other siblings are 6 yrs, 9 yrs, 16 yrs YOUNGER than me... It is really like having multiple families. My youngest sibling is more like my child (he's 14 this year)... But even with the age spread we are a VERY close family... What ever happens will be for the best.