Sensor guardian 4 - reliablity

I am struggling to get my Sensor to last. I place it in the back of my arm. Use new batteries to charge. However I seldom get 7 days. Usually 6 days.

However I often get 2, 3 or 4 days, Really disapointed at this reliablity.

I live in a hot climate, should I place the Sensor in the fridge ?

Suggestions please