Once the instrument is up to temperature, you have a working time of 1 hour before the next fill. The refill time depends on the evaporation of the LN2. If your lab is warm and the humidity is higher, the LN2 evaporation will be faster. If your lab is colder and the humidity is lower, the LN2 evaporation will be slower. You do not need to refill the LN2 tank until the temperature read goes below -80C.
