Someone told me the other day leave the lid "off" the mag box in the fridge, I did this and my maggots haven't gone all sweaty {Smile} but I bet as soon as I have to put a lid on them they will begin to do just that, no matter how much maize I add.
I always riddle left over maggot when I get home and they go into those Sensas green trays with fresh maize meal and into the 'fridge. Every day they get riddled again and put back into the 'fridge.
Really fresh maggot should last around 950°C hours . . . . before they turn to caster.
A standard 'fridge is set at approx. 4°C so they should last (900/(24x4) or around 9 days.
Now, I'm sure that there are people around who have kept maggot for much longer, or indeed much less time, but the above is a simple rule of thumb that served us very well for years when importing upto 25 gallons of maggot every 2 weeks into Norway, over a period of about 6 years.
You can get maggot to last a little longer by placing them into a poly' bag and expelling all the air then knotting tight. In about a day the maggot will go absolutely still and elongated, in fact they look totally dead.
However, once they are tipped into large trays and given a few hours they recover very quickly. Only problem then being that they don't last too long afterwards having been once "hibernated" like that.