I have been reading here the questions and answers regarding, de-tuning, or loosening the strings on a guitar every day at the end of each practice session. From the many answers it is clear to me that there is no need for this practice unless the instrument is stored for a long time. However, I wonder if this also applies to a mandolin, as I have a new bowl back mandolin, built in Italy, and I know that the tension on the neck is about 80 Kg, which seems enormous to me on an instrument which looks so delicate. I practice 2 hours a day and re-tuning and de-tuning every day would be quite annoying.
I've never untuned the strings of my bowl-back mandolin after playing. Admittedly though, I own it only for a little less than a year and I use ultra light strings (but the gauge should usually not matter for a modern instrument).
Another point to consider: If you think that the mandolin is an especially small and delicate stringed instrument, do not forget the violin. A quick Google search showed that violinists usually do not untune their strings after playing. If it is safe for the violin to keep the strings in tune when not played it should also be safe for the mandolin.