I have one that is probably 5 years old that is barely used and still in good condition. I have kept it in a ziplock bag. I have no idea if that helped or if I was just lucky but I wanted to rub your face in it.

Kidding!

I have no idea if it is possible to "rehydrate" the crayon that is wax-like, but have you tried taking it out of the foil and checking the condition of the bottom end of it?