How do you know when you have had your last baby?

I’ve had 4 pregnancies, 3 live births. We are late 30s, hubby will be 40 next month. Our kids are almost 4, 2.5, 9 months. I’ve never had an easy pregnancy so I thought I was done after our third, hubby kept talking about a 4th. Recently I’ve started thinking maybe we could have a 4th. However, prior to Covid my husband traveled 4 days a week, that would essentially leave me to do everything for the kids Monday-Thursdays. Our second has some health issues and we have so many therapy appointments that I don’t work. My husband makes great money, but a 4th would 100% mean I would need to go back to work full time (I’d prefer to go back part time in the next 6-12 months) to maintain our current lifestyle (daycare/preschool, college funds, swimming, soccer, vacations, etc)

What helped you make the decision? I know adding one is possible, but will it stretch us thinner than I expect and not allow us to do the things we want to do for our kids we currently have? I’m 1 of 3 kids, recently one of my brothers passed (almost 2 months ago) and only having 1 sibling feels lonely to me, like something is missing, maybe that is playing into it as well?