Can the PAXgene Blood DNA Tube be frozen? If yes, at what temperatures and for how long?

The PAXgene Blood DNA Tubes can be stored at –20ºC for up to 3 months. If tubes are to be kept at temperatures below –20ºC, freeze them first at –20ºC for 24 hours, then transfer them to –70ºC or –80ºC.
To freeze PAXgene Blood DNA Tubes, stand them upright in a wire rack or horizontally in a plastic bag. Do not freeze tubes upright in a styrofoam tray as this may cause the tubes to crack.