My experience with marshmallow is the best is 2 weeks. After 2 weeks its starts to get a bit spongy and not a fresh tasting. I've made caramet pecan patty's that have last forever so I guess it depends on the weather, humidity etc....fondant cream centers last about a month, is that something you might want to try? Peter Grewelings recipe for fondant is easy and you can add flavors like mint extracts or fresh mint and other extract and freeze dried friut powders. there are some companys out there that will send you free samples for the powders. google freezed dried fruit powders and see what you come up with.... Rena