Maiden didn't make a mistake. This Status Quo fan we-only-want-to-hear-the-hits mentality is ridiculous. You heard the hits last time. And the time before that. And if you didn't go last time you've lost out. After 30 odd years these bands aren't playing for people who want to hear the hits. They're playing for the real fans.
Priest will be playing Nostradamus in it's entirety at some shows. Rob Halford has already stated this. They will also be doing some Ripper-era songs.