Dry ice will last for about 4 days in the freezer. If you are storing it for a longer period of time, then it is best to buy an extra-large (2 pound) size and keep it in the freezer at all times.
Use gloves to protect your skin when handling dry ice, and store it safely according to safety instructions on the packaging. Use gloves to handle dry ice. Do not store it in an airtight container. Please also ensure that any rooms or vehicles you are traveling in are well ventilated.