Hi Iris,
It should be placed in the fridge if leaving it out for more than a couple of hours and should be consumed within 48 hours ideally once refrigerated.
I usually just make up one dose worth at a time personally because it tends to dry out and crust a little and I would end up forgetting it in the fridge, but you could make enough for a couple of doses and keep it covered for the 48 hours in the fridge.
With warmth,
Benna