Solids

I know the phrase "to do somebody a solid", meaning to do a favor for somebody or do something for somebody. Seems a little like it's peaked and fading as hip slang — I would have figured it for 1990s. Madison's free weekly, the Isthmus, is doing its local favorites content now and when you submit, you get a message with this:

Thanks for doing us a solid and voting for your Favorites.

Have we now reached the era when retro means '1990s'? Is this term more resilient than I realize? I do see a lot of occurrences specifically with voting in contests. Maybe it's developing into one of those things used only in a single collocation?

Oh, and by the way: They do have a "favorite local content blog" category. (The winner will get more votes than this blog has gotten in total page views, probably, but hey ... .)