I know Bakery story has something similar, if you leave finished food on ovens for too long (usually for the amount of time it took to cook it) it becomes spoiled. I figured something similar might happen here with soulmates and/or babies...

I picked a soulmate that would take six hours to arrive and went to sleep. After around twelve hours, I think, it wasn't there anymore, the game said that the soulmate had gotten tired of waiting and left.

Has anyone figured out how long can you let a soulmate (and babies, too) that has arrived wait before it leaves?