I have yet to fill it up! I only have 2 for now, one not being mine and I had another one that sadly died after 2-3 weeks, so I cannot really say.
Though taking care of the individual snakes each in their tubs in different rooms (quarantine) does not take more then 15 minutes if I don't play with the snakes. In a rack I suppose it would be a little more since I'd have more but being all in the same place it is just to slide the tub out, change substrate (paper towel or newspaper) and change water. Though I do take a few minutes morning and evening to make sure all temps and humidity are ok but again in different rooms so longer then if they were all in the same room.