Starting a big family late?

Can anyone share experiences of being closer to 40 with a big crew? My three kids are 5 and under and we’re planning number 4. My concern is whether I’ll feel done after 4. We’re 35 and I just think sometimes man we should have started before 30. I know I didn’t have the same mindset then, so it wouldn’t be the same. But did anyone else do something similar?