I recognize this very much, and I do it myself.
Dream Theater is a good example. I don't think they have done a really good album since 6DOIT. There are a few good songs spread out on the albums afterwards, but none of the albums themselves have been solid all the way through. Octavarium, Systematic Chaos and Black Clouds are on the edge of being almost bad for me, but ADTOE was a nice improvement.
Metallica is another example. As I see it, they've made one good album in the last 24 years, and that is Load. Everything else is pretty mediocre, but I still check out their new stuff when it comes, because I consider Ride the Lightning, Master of Puppets and Justice to be classic albums. With that said, I haven't checked out Beyond Magnetic though.