How long will the “RT-96” Cool Cube™ last? L How long will the “RT-96” Cool Cube™ last? When properly conditioned, the RT-28 will hold temperatures between 20°C and 24°C for 56+ hours. Post navigationPrevious post: How long does it take to get the “BT-96” Cool Cube™ ready to hold my vaccine?Next post: How do I prep the “RT-96” for use?