A freezer is not an appropiate place to store dry ice. At some point the pressure it creates will pop the door open and if it is at night you may lose food not next to the dry ice.
The best storage solution is a styrofoam cooler and blankets, newspaper, towels or other objects to keep air away from the ice. Even in the best of cases you can expect to lose around 20% a day. Back in the day when I was partners in F & B Manufacturing (we built over a thousand 55 gallon dry ice fog machines) we were also a local distributor for dry ice.