If they are individually bagged how long will they stay good for? i want to start making some things ahead for Farmer's Market. Can they be frozen and then thawed?

I don't think they can be frozen, but give it a try.

Once the mm's are covered completely in chocolate, they should last for a couple weeks, at least.

I really can't tell you an exact answer, they don't last long enough here at my house to experiment. And for my clients, they don't let them stay around either. I would say that if you have them in individual bags, they should last a couple of weeks (probably no more than 2) but, I wouldn't freeze them.