A bunch of us go together each year and buy waxies in bulk. I keep mine in my basement (probably 50 deg or maybe a little less).
I keep the lids either off of the waxies (they dont try to escape) or at least loose, and I pick through them every so often and if I find any that are going bad, I try to use them on the next trip.
Have never fed them or changed the sawdust, but that might be a good idea.
We got them last year in mid december. I used the last of mine on the opening day of PA trout season, which is mid-april, although I must say that we used most of them in December/January.
One of the guys tried to keep his in the fridge and they only lasted about two weeks before they all turned black.
I hope this helps you out. We are putting an order together now -- if you live in central Pa, pm me if you want some :-)