2 under 2, thinking ahead for #3?

So to start off I'm only pregnant with #2, but I'm wondering how others did it when it came to the next baby (if you have 3 kiddos). Did you wait a little longer? Kept them the same distance apart? My son will be 21 months when LO #2 is born and we're throwing around the iffy idea of a third already. We're definitely going to wait and see how everything pans out after baby #2 is born lol.