Well here it is still very much winter and cold.
I have 2 litters that are 4 weeks old today. One I took the nest box away
but I gave them a plastic box so they could sit in that. It is real
close in size to the nest box. The other litter I probably will do the
same with them in another few days. But only because I need the
nest boxes for other does that I have expecting real soon. These 2
litters I have in the big plastic dog crates that I call the maternity
cages. The babies snuggle together in the hay. The box is their safe
zone. They can be out eating and if I get too close to the door, they
run and jump in the box. As long as the box is kept clean, I don't
see any problems with leaving it in for a longer period.
I do put a shorter box in front of the nestboxes so the babies can
climb back into the nestbox. At 4 weeks now, they don't need that
step, but I also use it as a feeding platform for their bowl of
oatmeal.