I know this doesn't relate directly to your question, but IMHO I think it's best not to keep a lot of dried spices around. If you can find someplace that sells bulk spices, just buy as much as you need to get you by for a while. Stay away from those grocery store jars of spices. Of course, if possible, buy fresh. Again, IMHO.
Actually, I plan to dump my grocery store-bought spices and buy from Penzey's, but there are some I don't use often (but still do use) like Allspice. So I just wondered if I could extend the shelf-life by freezing instead of just keeping them in the cabinet.
Also, is it better to transfer spices sold in little, plastic bags to plastic or glass containers? Or do the bags do a better job of keeping more of the air out?
I transfer all of mine to jars. I had an unfortunte experience once with a very fragrant cumin. I didn't have time to put it in a jar and just kept it in the plastic bag with twist-tie and threw it in the cupboard. Also located in the cupboard was my confectioner's sugar. A couple days later I made a cake icing using the sugar and wouldn't you know it, the icing tasted like cumin!