Judas Priest... maybe.
Now, I love JP. I mean love. For my money, the greatest band of all time- not just metal band, greatest band. However, as much as I liked Angel of Retribution, it just wasn't as good as their other albums (for the record, by the way, I loved Point of Entry and Turbo). Aside from "Deal with the Devil", I don't think any of the songs from that album really stand out. The reason I think that they should maybe stop is, aside from the fact that they're pretty old, I'd hate the see them really start to slip. Sure, some would say that they already have, but it'd kill me (maybe even for real, folks) if they slipped to a Metallica-like place. If the upcoming album insn't really good- say, Ram It Down good- I think they should call it a career.
Of course, if they could harness time travel and go back to release a few more 1970's albums, I'd be all for that.