There are also some downsides to keeping it damp. It will then continue to break down and possibly compact too much, and you may get insect nests and fungus which is not necessarily a good thing, that's potentially the same fungus that causes damping off. To rehydrate dry soil it just needs to sit in the pot with some water added for a while, it may not soak it up immediately but over a few hours or days at most it will.
This year I found an old stash of potting ingredients that were my mother's and added those to a few pots. The stuff must've been two or three decades old and was stored bone dry. I see no difference in the health of those plants for better or worse.