I'm SOOOOOOOO obsessed with Light Year too. I only bought one back up (but I NEVER backup anything) and am contemplating getting a second back up. It's just perfection in a pan. I think I'm heading to the mall on Friday, so if I find a MAC with some in stock, and can hand pick one more, I might just cave if there is a beautiful swirl.
And to comment on the difference swirls make, I almost didn't get CoU because in the store I went to had it had this gigantic orange swirl, and that one just showed up so, so orange on me, so I passed. But I wanted the whole MSF collection, and it kept bugging me so I ended up ordering it, and the one I ordered has a bunch of gold between the swirls, and not much of the darker orange swirl, and it is beautiful!! Shows up like a lighter version of NARS Luster on my cheek.