Be aware that zip-lock bags may not be perfectly air-tight or probably humidity-tight - but much better than nothing.
I have a food vacuum bagger, and have vacuum-sealed zipper type bags and placed them in the refrigerator, where they do not maintain their tight fit, i.e. air is seeping in.
I haven't done a study, but bags tagged for the freezer should be better, I know they are thicker.
"America's Test Kitchen" tried various bags, and liked the Ziploc brand double-zipper freezer bags. To my amazement, a spool of filament "just" fits a gallon bag (YAY!).
If you can get true food-vacuum bags large enough for a spool for long-term storage, this is the best way.
I was pleased to learn what I SHOULD have known, namely that UV can be a factor -- and until right now had been storing my filament inside an east window that gets sun.
Calcium chloride is an excellent desiccant - often sold as a "closet dehumidifier", or in cold climates, as a very inexpensive by-the-bag ice melting "salt" (check the ingredients).
In absorbing moisture, the CaCl2 puddles, and is harmful such as to leather, so be sure you empty the liquid and refresh the crystals occasionally.
A US$7 humidity gauge may be purchased (Amazon, eBay, etc) and placed in a container with filament and desiccant to see how it is doing.
/Ward C, inventor of Xmodem & BBSs