Yes, Xell, I agree. I didn't mean to say that you need to absolutely replicate what they are doing, but that you pretty much can't go wrong with relatively normal fridge temperatures if that is what the professionals are doing.
I think that another plus for the fridge, apart from it being cool and dark, is that the temperature consistently stays the same.
That being said, I have not really tried to keep Japanese green tea in, say a living room, for a year. I have however kept it in the fridge for more than a year and have not experienced any deterioration of flavor or aroma whatsoever.
I have never kept open teas in the fridge for fear of moisture. It can probably be done properly if some precautions are taken.
It's probably not necessary, though. Drink that tea!