I got pregnant with my 1st and 2nd child, after 35 years old.
Got pregnant naturally each time.
It was a good normal pregnancy.
But, I did have a 3rd pregnancy, but that ended in miscarriage.
My kids are 4 years apart.
Just so happened. It is great.
My kids get along, my daughter was at an age to adapt well and not a baby herself etc., when I had my 2nd child.
It all depends on how the siblings get along and adapt.
An older child, will still need attention too.
But, they are more 'mature' by then, if a baby comes along.
They can also help.
But always be aware of age related phases/development.
My Husband and one brother are about 6 years apart. The other brothers are much older. They all get along.
It also depends, on how you, incorporate your eldest child, into the new realm of having a baby around. They need to adapt too. And how you teach the children... about what a sibling is, what a new baby is, how to make the eldest child not feel left out, etc. And how to ALLOW, the eldest sibling/child... to also have their own things, and not 'have to' share everything, by default.
Not expecting the eldest to be an 'example' for the baby or younger child. But to be a part... of things, too.
An older child, will have their own needs/phases/and be more independent too. They will need, their OWN alone time too etc. And their own activities etc. And their own routines. Because of the age difference. The interests, of the eldest child, will also be different.