I saw an old discussion on salt air causing rust on reeds. Humidity can also be desastrous on reeds: i own a Harry Crabb concertina, bought it new in the 70-ies. one of the "lessons" Mr. Crabb gave me as starting player was: This instument won't need any maitenance for at least 20 years to come if you use a soft brush to clean the bellows' folds regularily, and especcially: "When you come out of the cold, first draw some warm air from the room in to the instrument. You'll avoid the reeds getting condense setting down on them and cause them to rust in the long run". He was quite right, i promised to do that, who could resist such good advice, and they're still perfectly in tune, 35 years down the road ...

Good point my friend.

If I ever play my box outside on a humid day I try to always run air conditioned air through all reeds before putting the accordion to bed.

Cold days I do the same.

Have you ever noticed that reeds sound best when played in an air conditioned room? To my ears it almost sounds like a better instrument.