Robert Plant says bands who stay together for "20, 30 or 50 years" are "hanging onto a life raft".

The 73-year-old singer rose to fame as the frontman of Led Zeppelin, forming the rock group along with guitarist Jimmy Page, bassist John Paul Jones and late drummer John Bonham in 1968.

After conquering the globe, the 'Whole Lotta Love' rockers split in 1980 in the wake of Bonham's death, reuniting for a few concerts in 1985, 1998, 1995 and 2007.

Plant never wanted to stay in the group decade after decade like other acts such as The Rolling Stones have because he has always yearned for new musical challenges and never wanted to look "sadly decrepit" on stage rehashing the glories of his youth.

And that's what he has enjoyed about working with bluegrass singer Alison Krauss.

In an interview with MOJO magazine, he said: "The good thing about Alison and I is that we're a couple of kindred spirits.

"Most musicians form a band, then they stay in the band until it's over - 20 years, 30 years, 50 years, whatever it is, and it starts to look sadly decrepit. It's like people hanging onto a life raft, or staying in a comfortable place.

"With us two, there's nothing written in blood. We were ready to do something new, and we knew how good it was before, so we can just join up again and see where we go. We've got nothing to lose."

Plant and Krauss have reunited for a second album, with 'Raise The Roof' - which comes 14 years after their first collaboration 'Raising Sand’ which won five Grammys - being released on November 19.

The 'Stairway To Heaven' singer believes he and Alison, 50, work so well together because they come from completely different musical backgrounds and worlds.

He said: "When I spent that first year or so with Alison, I was so amazed by America. I thought I'd got America down, but here was this whole world of country music I'd not encountered. That's the great thing about me and Alison - we're ably supported by a world of beautiful music that one of other of us doesn't know too much about."