I usually make a frech batch of MMF for every cake but this time I dont need so much and I have left over from 4 weeks ago. Can I use it? It has been wrapped in saran and in a ziploc.

I have and it was fine. All that's in it is marshmallow and 10X so there really isn't anything that could spoil. Just taste a small piece and make sure that it hasn't picked up any off flavors or staled. Happy baking

Mine is a lot older than that and it is fine. Go for it.

I think it will be fine. I would put it in the microwave for a few seconds to soften it and knead in a little Crisco. Sometimes I think the older fondant tends to dry out faster though (once it's placed on the cake and is exposed)...just my past experience.

Thanks guys