I really shouldn't say "long-term" storage because these are dry foods that I use regularly, and I probably don't have much over a year's worth of any of them. But since I don't know how long it is going to take me to use them up, I am storing them as though it will be long-term, as in 5 years or more.
I had 50 lbs. of flour and 20 lbs of rice in my small chest freezer, plus a few 2-lb bags of beans and rice. I ordered a pack of 30 mylar bags and oxygen absorbers. The mylar bags are 4.3 mil. I used 5 mil bags previously and was curious whether the 4.3 mil bags would be thick enough.
I packed the flour first. That can be messy. I minimized the mess by opening each 5 lb. bag, slipping the mylar bag over it, and then turning over and slowly emptying the flour into the mylar bag. I shook the flour down as much as possible, and folded the mylar bag over to push as much air out as possible and added 1 oxygen absorber for each mylar bag. Any little jiggle of the mylar bags made some flour dust on the area to be sealed, so it seemed hopeless to get the seal area totally clean of flour dust. To ensure a good seal, I first sealed the bag very close to the product, and then I re-cleaned the remaining part of the bag and sealed it. So each flour bag has a very wide seal.
Each 5 lb. bag required its own mylar bag, so that was 10 bags worth. I've been getting buckets from my local Dillons bakery, and was able to put 3 of the mylar bags into each bucket (15 lbs. worth of flour). That took 3 buckets with 1 extra bag in a bucket by itself. I use the buckets to make a shelf in my living room -- 6 buckets with 3 buckets 2 deep.
I also did the smaller batches in PETE bottles, using one oxygen absorber with each bottle. That went pretty fast. I had 3 used #10 cans that I filled, put in an oxygen absorber, and then covered with mylar and the plastic lid. I then used duct tape to tape all around the lid and totally covering the mylar extending below the lid.
I put my left over oxygen absorbers in a canning jar, but the lid wasn't sealing, so I became paranoid that I was going to lose my oxygen absorbers. Waste not, want no. So I went ahead and did the rice in the mylar bags. I used 2 oxygen absorbers in each bag in case they weren't still good. I got the 20 lbs of rice in 4 mylar bags. I put two of the bags in another bucket with rice, and the remaining 2 in the bucket that had just 1 flour bag.
I checked them later that night and they looked like they were all going to have good, vacuum-packed seals. Vacuum seals are not necessary with oxygen absorbers, as there can still be air -- it just won't have oxygen in it, only nitrogen. But like other preppers, I'm paranoid about getting good seals. I checked them again the next day, and they looked very good.
So my conclusion is that 4.3 mylar bags are indeed strong enough for the products that I seal -- even the rice, with its pointy ends, didn't cause a problem.
If we had no winter, the spring would not be so pleasant; if we did not sometimes taste of adversity, prosperity would not be so welcome. Anne Bradstreet
And if men come unto me I will show unto them their weakness. I give unto men weakness that they may be humble; and my grace is sufficient for all men that humble themselves before me; for if they humble themselves before me, and have faith in me, then will I make weak things become strong unto them. Ether 12:27
Yea, all things which come of the earth, in the season therof, are made for the benefit and the use of man, both to please the eye and to gladden the heart; Yea, for food and for raiment, for taste and for smell, to strengthen the body and to enliven the soul. And it pleaseth God that he hath given all these things unto man; for unto this end were they made to be used, with judgment, not to excess, neither by extortion. D&C 59:18-20