I have MMF that I made about 4 months ago. It's hard like rock. If I put it in the microwave for a few minutes to get soft, will I still be able to use it. Or should I make another batch.

make another batch!

I agree, make another batch; 4 months is too long

MMF keeps for a long time. if it was wrapped good it should be fine. If you microwave it and it doesn't feel right, then make another batch.

That stuff lasts a long time. Four months may or may not be too long, if it was properly sealed up as SPCC said - honestly I would just taste it. If it tastes (and smells) fine, I wouldn't hesitate to use it after microwaving it to soften it up.

Update, I put the fondant in the microwave to soften. It tasted great, however after the fondant cool down it became hard again. I kneaded and kneaded the fondant. It was so hard I needed iron arms. I throw it out and made another batch.

Thanks for the update. I was curious.

I found a batch that I had made a while back and it was well covered but you could feel like a hard shell formed on the outside of the batch.... soooooo

I took a carrot peeler (yes a peeler) and peeled all the hard stuff... then I nuked (sp?) for 30 sec or so.... knead with some shortening.. and it was perfect... no hard pieces... didn't have any problem at all after that... so now if I have some colored fondant that I had saved form a previous project... I peel the skin (just like you would a potato) and nuke it and it's perfect again...

hth