I've keep them a live for as long as a week. They were keep in a paper bag with some grass then put in a plastic bag. Leave the plastic bag open and place it on the bottom self of frig. turn the bag every day. When fishing keep them in a small cooler with some ice on the bottom covered with a heavy towel. Don't let them get wet. You can use them for several trips if you keep them this way. Be sure your getting fresh worms when you buy them. The fresher the worms the longer they last and be sure to tell the bait dealer to put plenty of grass in the bag.
I buy bloods a flat at a time.On the boat I keep them in a cooler on top of two bags of ice, and iI keep moving the cooler to keep it in the shade. At home They stay in the bait fridge in the garage & I turn the flat every am & pm. If they don't get used up they can last a week.