ok, so i baked them, cooled them...all the way (i thought) but when i placed them in a container they almost automatically became sticky.

how long is "too long" to let them air and dry before they begin to dry out??

please help

That is a good question. I have had that happen to me as well when I place them in a container overnight. I think it is due to the fact they were still a little warm. The next day I went ahead and piped icing on them. I did not let them sit out because I was worried the cupcake would dry out, so I decorated away. They still tasted ok, it just may be a little difficult depending on how you plan on decorating.