I've been putting them in a zip lock bag and then pouring a little distilled water in the bag and then sealing it up.
I just leave them in there until I need 'em. By the time I pull 'em out, they feel about the same as when they were new. But.... it's not like they are just sitting in a pool of water. I pour in just enough to do the trick. If I get too much water in there, then the next day I will pour out the excess.
Not sure how many times you can do it. But, it works for me.