I'm pretty sure they will keep for several weeks to months if they are sealed, and stored in a cool, dry place.
I'm planning on making some chocolate covered oreos (and Nutter Butters - I stocked up when we were on holiday this week in MI) (boy, I wish we could get them in Canada!) to give away at Christmas, and I'm planning on making them probably the end of October, early November.
When you think that chocolate companies make and ship their chocolates with a shelf life of up to a year, I think you'd be pretty safe in making them ahead a little...
