Not operating can be hard on tubes because gas (that leaks through the glass) can accumulate. High temperature may speed up the gas accumulation. Operation of the tube cleans out gas.
However 3 months is not that long, and 120 degrees is not that hot, so I would bet that your tube failure was just a coincidence.
However 3 months is not that long, and 120 degrees is not that hot, so I would bet that your tube failure was just a coincidence.