How to best store not-yet-used frying oil? I occasionally deep fry using peanut oil. The small amount used in my deep fryer (around one quart/1 liter) is easy enough to store in a polypropylene container that came with the fryer. Originally, I was storing it, after filtering, in the fridge, but it'd still develop off flavors within a month or so. After Cook' Illustrated informed me (sorry, subscription required) that freezing works, I started freezing it, and it does indeed keep the oil fresh much longer. A quick run through the microwave warms it enough to dump into the fryer.

Unfortunately, refined peanut oil is sold either 1 gallon (~4L) or 35lbs (~15.8kg) containers. Those do unfortunately go rancid once opened—even if stored in dark place. Of course, 35lbs is half the unit cost (but is way more than I'd use before it goes rancid, if stored in its original container). 

I'm wondering, is a good way to prevent unused peanut oil from going rancid? Would something like 1qt mason jars, with the lids vacuum-sealed on, help (stored in the pantry)? Alternatively, are there some additives that would help (and not prevent its use in deep-frying)?

Getting a gallon in the freezer is possible, but 35lbs is way too much freezer space.
It should be stored in a cool-dark place. Your cupboard is just fine. 

You're overlooking an important distinction in the Cook's Illustrated snippet: their oil is used. Used oil is already damaged by the high temperatures required for frying, this greatly shortens its shelf life and makes it much more prone to rancidity. Storage of used cooking oil is covered in other questions here:


Frying oil reuse
How to keep deep frying oil usable?


For peanut oil specifically, the shelf life is two years if unopened and one year if opened.

I have a nearly empty 10-14 month old bottle of peanut oil in my cupboard right now. I used it last night, and it showed no signs of rancidity.