You are making the assumption there is a difference in processing among brands. Is the expensive stuff processed, transported and stored any differently than the cheaper brands? If you think so, do you have any evidence?
Rancid flax oil is easy to spot. It tastes terrible compared to fresh flax.
Fish oil is usually encapsulated, which reduces its ability to oxidize. Still, I keep the bottle in the fridge if it won’t be used soon. This probably isn’t necessary, but without the rancidity taste test available I’d rather err on the side of caution.
Still, I have no control of the conditions under which the fish oil was processed, transported and stored before I bought it. I’d think the best policy is to buy from a retailer who sells a lot and is therefore receiving fresh stock regularly.
Yes of course I have evidence about different processing techniques. But now I am running into specific name brands, and as I mentioned I am now biased.
Rancidity in fish oil is also pretty easy to check. Try cutting open a typical 180/120 pill and taste the oil, as compared to one of the ultra-refined brands.
I think it's the woman's job to tighten up to fit her man--it's lots easier for us.