Tee Cee,
When you get home after fishing:
Take the maggots out of the bait box and place in a large tray (Sensas make 2 sizes, both excellent)
Then, riddle the maggots, twice, to ensure that there is no left over maize meal.
Place the riddled maggots into a second (clean and dry) tray, and add a little fresh maize meal, and place in the fridge. Don't cover the top of the tray.
Every day riddle the maggots off again and add fresh maize meal if necessary.
I try to get mine from the shop on 'delivery day' which in my area is Thursday/Friday.
They should last approx. 900 degree-hours if bought fresh.
So, kept in a fridge at 5 degrees they should last, if riddled and kept clean, for about 7 days, (minus the daytime temperature/hours on the day you used them)
As for caster: I keep mine in ordinary bait boxes with a plastic sheet cut to fit the top plus about 3 inches over. Place the plastic sheet onto the top of the box then fix the lid. Keep in the fridge but give them an hour a day without the plastic sheet.
The above has worked well for me; I used to import a lot of maggot and caster (every second Friday) when I lived in Norway both for sale and for my personal use. These methods never let me down and I always had good fresh bait.