Really necessary? No, but, why take a chance at having plastic-based chemicals leach through the mylar into your food and causing a bad flavor? Personally, I prefer sealed bulk-sized stainless-steel containers for storing my food, but, they are difficult to locate sometimes ....
Leaching is very normal. If you put dried peppers into a mylar bag and flour into another one and put them side-by-side, after a while, the flour will start to retain some of the pepper scent. It might not happen after 6 months, but, maybe 6 years or 12 years. The pails themselves can produce scent of their own - I have some pails in my basement that originally contained foods and after a few years of sitting around empty have started to emit an oder ... I know the smell of TupperWare from a mile away and the smell of "old" TupperWare is much stronger than the smell of new TupperWare. RubberMaid containers have a different scent - I know them too. Tonight I was at the back of the house and all of a sudden I could smell Peanut Butter. WildMist decided to eat one of the peanut butter / chocolate chip cookies that I baked yesterday. She was close to 60' away and I could still smell it.
My rice, blk bean, sugar, salt and a couple of more items I keep them inside of mylard bags and the bags inside of those 44 red gallons pickles barrels from Greece.........I also sucked out all the air out of the barrels after the food was inside.
