I think it depends on circumstances. There's plenty of old farts just doing the rounds with greatest hits tours (Specials, Stone Roses) and lots of solo artists that ran out of ideas years ago so resort to covers albums (Weller, Stewart, Costello...). Personally I'm not a fan of that last Cash...
Really, really don't this works. The music's okay, a bit gentle by their standards but the lyrics are appalling.
http://pitchfork.com/news/56869-the-who-reference-daft-punk-with-be-lucky-a-new-single-from-forthcoming-definitive-hits-collection/
And the new greatest hits album cover that...