Preserve the supply of mylar?

Not sure what you mean. We order it in bags of 2 sizes. It's shipped flat, with one rounded fold maybe, in the middle (no sharp folds that create pinpoint holes. Just store the bags in a covered plastic container, away from heat and moisture, sun.

Storing the oxygen absorbers is important too. You can feel them begin to heat up as soon as they're exposed to air. So you take what you need out of their original packaging and then wrap and tie that pkg to get the best seal you can so they'll absorb the oxygen in the bag and shrink it down again. They should be used within a year after opening.

We put the mylar bags in 5-gallon buckets, fill with grain, heat seal the tops of the bags. The rigid plastic of the sides and the tops of the buckets serve as protection for the bags, so they don't get punctured.