Deciding to have another babe?

Since the birth of my newest baby, I have gone back and forth with the decision of having another down the road. Ideally we’d start trying when he’s around 9-12 months. I’ve always wanted three or four children but after this second, it has been rough. Mainly the inconsistency with sleep is really beating me down. We’ve tried a lot of different approaches and have had a few good nights but just nothing consistent. How have some of you managed two under two and the sleep? My oldest is 7 so I have basically started over. We want to start trying when the youngest is between 9-12 months but I don’t want to be literally dead from lack of sleep with a third 😅😅