I had 2 years and 2 months between my 1st and 2nd babies and again between
my 2nd and 3rd babies. I then had a gap of 4 years exactly with number 3
and number 4. I preferred the small age gap - I find they have more in
common when they get older and play together really well. I find 3 and 4
(both girls) are a little too different in their age range to do much
together yet.

I've observed the same -- just based on most of the siblings I've known
and from talking to other parents, closer gaps (2ish years) tend to
produce closer playmates, especially in the early years. But there are
exceptions everywhere and no kind of gap is a guarantee that you won't
have issues either related to being too close or too far apart.

IIRC, Ericka's posted the cite for a study saying that the optimal time
for conceiving, from a straight statistical health standpoint, is
between 18 months and 23 months. But being that you're up against the
"over 40" issues, I'm thinking that's not as big a deal as the possible
fertility stuff you may start running up against. IMHO I don't think you
should wait unnecessarily, as long as you feel up to conceiving again
after six months, paying special attention to calcium supplementation
and so forth.

Good luck!

Mary S.