How do I stop my Crispie/Crispy cake from going stale? I make a Crispie type cake, but with my own homemade ingredients, Mallows,etc when I make it with shop bought Marshmallows etc it lasts for weeks, when I make it with my own ingredients it goes soft/dry, the crispies loose their crisp and the gooeyness goes. How do I solve this? Would thicker packaging work? or vacuum sealer. At the moment they are just on trial and are being ept in thin "boil in a bag" vacuum packaging for home use. 
Can anyone give me any advice that might help me please. 
Thank you Sarah
I usually store them in an airtight container, with wax paper underneath each layer. They keep very dry stored like this. It could be that your bag is not sealing 100%