I made some for the first time today, chocolate and corn syrup.
How do I store it and for how long will it keep?
I wrap it in plastic and just keep it at room temperature in a covered tupperware container. It keeps for a long time, but it will dry out after a long period of storage (I'm talking months.) I microwave it for 10 seconds if it gets too hard to knead, then knead it again when it softens a little. If you overwork it it will get oily, though, so watch out.