Also, anytime you "change" the seasoning type, in order to actually get whatever the benefit or characteristic of the different oil, you have to remove all of the existing seasoning ... highest heat and take everything off, right down to the light gray metal and then immediately coat with oil and begin seasoning before too much air gets to it.
So when you buy a new Lodge for example, it doesn't really matter what oil you use; you're still bound by what Lodge seasoned it with unless it becomes rusty. Everything else will either come off or give various lubrication results and still not stay on as well as it might otherwise, if it were the only oil on the metal.
Yes about flaxseed oil insofar as the refrigerated kind is what to use (NOT the stuff sitting out on the shelf sold at the health food store). Unfiltered, high lignon ... but a waste of time and money in some cases. I have some bought at Whole Foods, their "365" brand, best used by Aug 2015 but still fine. Although it has a flip-top, it's actually sealed, kinda like some of the newer ketchups that have a membrane in the lid. So you squeeze it out through the membrane's slit, not pour.