If the SE is a dupe neg and the original is untouched, it has 18-20 more years of degrading that they would have to fix. Or the pieces cut out of the neg to create the SE (even now that sickens me) would probably have needed a lot of work. Empire probably has the same fading issues, and hopefully Jedi was relatively easy.
The good news buried in that Gareth Edwards Rogue One article is that the negative of all the unused negative was just fine, and usable to boot.
The “unused negative”, what do you mean by this?