I'm not really an expert but I believe if you keep them pretty airtight they should be able to last up to 6 months. A good (and cheap way) to keep them is to get one of those reynolds food vac things (they are like 10 bucks for the initial package and the bags are cheap after that). It doesn't work as good as the big food savers but its relatively cheap and easy to use.

I don't know much about the fuzzies - but that doesn't sound good. When I thaw out my frozen feeders I put them in a bowl of hot (not boiling) water until when I feel up under their ribs it is warm and I'm sure they are fully thawed. Then I wrap them in a paper towel to dry them off - my guy always goes for them but some people also use a hairdryer on them for a few minutes to make sure they are extra warm.