My director would like to store dry ice for occasional sample send outs. Does anyone have a good, small storage container that they would recommend. If you do, approximately how many days does the dry ice last?

We save the dry ice we get with frozen blood products or tissues in a Styrofoam box with a lid in our deep freezer (-60C).  Lasts a week or so depending on how often it is opened, how full it is etc.

We store dry ice in a box that we get frozen tissues in - heavy duty, dense solid foam box with a dense, soft foam plug for a lid. The box is sitting out in the main lab at room temperature. Dry ice lasts for days in there, even with the foam plug off. These boxes are actually much better than the fancy cooler that we had previously purchased that was made specifically for that purpose. When the foam plug gets ripped up from being pulled in and out of the box, we just toss the whole thing and start with a different box.