I haven't had the chance to check extras in the Gold Edition Box yet but I'm getting that none of them are anything recycled from the previous DVD releases, so if one owns both DVD sets, he should keep them all for a good number reasons.

The biggest one: extra features are simply different. Some things in the previous release are not in the last one at all, like for instance, audio commentaries to episodes, which is a thing the Gold Box got totally deprived of, am I right? There is no mention of this in the back side or elsewhere...

I'm keeping them all, also for value and monetary reasons.

Also, you can loan someone your S2 set without worrying too much about the condition when it comes back.

Yeah, it's an alternative. I could be burning my favorite extras from season 1 and season 2.2 all into one DVD and then sell or just give away the green ones to someone and keep my golden precious!

But I will probably keep them all. In the end, my father is an intensive reader and some books of his, the ones he loves, he just keeps buying them again whenever they are translated by a different author. I guess it's the same thing for us.