I understand trying to plan somewhat, I am just saying that you can't really micromanage it down to a couple month's time span-especially when there is only a small window of a day or two each month where you can conceive.
Your friend has a 3 and a 9 year old who hate each other...but I have a 2 and 9 year old (similar age gap) who adore one another. That completely depends on the individual personalities of the children, which we have no control over.
I wasn't saying that you would have a problem conceiving...just that part of it is luck. People can use ovulation predictors and get lucky on the first try...and for others it can take much, much longer.
My youngest (the 2 year old) was a "birth control baby". He was conceived while we were being safe. (We had a girl and a boy, and we were DONE having kids...) On the other hand, I have a close friend who is trying to get pregnant, and it has been almost 2 years and nothing yet. (She and her spouse have both been to the doctors for fertility testing to rule out any problems.) They just haven't got lucky yet.
You can plan...and I understand planning...but it's gonna happen when it happens.