Metallica see "no end" to their careers.
The 'Enter Sandman' rockers - who formed in 1981 - have no plans to stop recording and performing but drummer Lars Ulrich admitted he hopes someone will tell the band if they no longer have "the physicality" to deliver a successful show.
Speaking to MOJO magazine, he said: "I see no end to it. The only question is, 'Does there come a point where the physicality the music needs is still there?
"I hope that somebody around me will go, 'Hey sunshine, maybe it's not there anymore...'
"Of course, there's a few people who think it has already happened. That's fine. But when we play the Kansas Cities of the world and you see 19,000 people connecting to the music and us connecting to them, I can tell you it definitely hasn't happened yet."
The rockers - Lars, Kirk Hammett, James Hetfield, and Robert Trujillo - acknowledge they are all very different people but they still feel like "brothers".
Kirk said: "There are people who want to divide and conquer. We're not gonna be part of that platform."
Robert added: "As individuals within the band, we're all different. But we get along. Different upbringings, but we are family, we're brothers."
While James dismissed suggestions his relationship with Lars has mellowed over the years, he admitted they realise there is "no use" trying to upset one another and regard each other as enemies.
He said: "We know there's a nuclear option and we know where those buttons are but there's no use pressing them.
"We are there for our similarities, not our differences. You don't need that enemy there all the time."
tagged in James Hetfield