I had first at 39 and second at 43. No problems conceiving. I did pay for a private CVS test for each though, as I wanted to be as sure as possible that everything was fine.
Worked up to my due dates.
Had 2 uncomplicated deliveries, (both on Saturdays), and was back at home very quickly, and driving DH to his work again on Monday. No relatives around to help at all, so I just got on with it. I would have liked some help, but it wasn't an option. Story of my life.....!
I don't remember feeling particularly tired - I mean I WAS tired, but perfectly able to function. I was pretty careful with my health and weight gain during both pregnancies, and was back down to my normal weight within a month.
And yes, I know this makes me sound like a smug, self-congratulatory cow, but it's still true!
OP, I think all you can take from threads like this is that everyone is different. Good luck with what you decide to do.