Do you need to get back to your brewing Potion at exactly the right time or could you also finish it e.g. the seguinte day?

You have an hora and 20 minutos to do part 2 after the gap of 80 or 100 or whatever minutos between the two halves. If you don't start the segundo part of the potion within that hora and 20 mins, the potion screws up. So no, you can't leave it for the seguinte day.

I can't even find the potion I have brewing at the moment, is that normal if the time's not up?