Should we have more than one?

Has anyone out there chosen/is choosing to have only one child? What’s your reasoning?

Hubby and I have a perfect 9mo old daughter. I’m about to be 39 and he just turned 43. We’re contemplating having another before it’s too late, but we are also really scared to roll the dice. Plus, the one takes SO much energy from us. We both work full time. But then again, the thought of her being an only child is scary too.

I don’t know what to do. If anyone has any words of wisdom when it comes to only children, it would be greatly appreciated.