Backed by radio play - BBC Radio 2 especially loves them - and TV appearances ranging from Paul O'Grady to Later... With Jools Holland, sisters Allison and Catherine finally had the success they'd been dreaming off.
It was their fourth album and came at a point in their career where they felt they'd toiled for long enough without anyone listening and were just about to go their separate ways.
Now, with that success under their belts (You & I peaked at No4 in the charts and sold more than 100,000 copies) it was time to make a follow-up.
"It was supposed to be out ages ago," says Catherine, referring to the forthcoming Creation.
Even though the pair finally thought things were going their way, they hit a huge bump in the road.
In 2013, they teamed up with a producer to start work on what would become their fifth album. Despite being confident with their songs and the producer having "lots of talent and a great reputation", they spent six months recording, only to have what they'd done knocked back by their record label.
"It went well at first," says eldest Pierce, Allison. "It's hard to put your finger on why something doesn't sound right, but you know it doesn't.
"It didn't have the energy or the emotion or life that we wanted it to have, and the label agreed.
Neither Pierce will say who it was they were working with, although they say he's worked with "loads" of big-name bands and made many great records.
"Working out what to do took a while," says Allison. Catherine, meanwhile, went travelling, to South America for a time, where she took part in an ayahuasca ceremony. Ayahuasca is a brew made from the banisteriopsis caapi vine, known for its divinatory, hallucinogenic effects and is traditionally consumed by Amazonian Peruvians.
"We all felt like we were in a really delicate place," says Catherine. "We were scared we were going to get dropped, scared we hadn't written the right songs, and then we did ayahuasca and it put everything in perspective."
Born in Birmingham, Alabama, the sisters travelled all over the States with their family while growing up, and were encouraged to pursue artistic creation by their "old hippy" parents, all the while being raised on a diet of Joni Mitchell and Bob Dylan albums.
Their background shows in their music, which has always had a American West-Coast vibe, while their close harmonies and vocal styles recall Rumours-era Fleetwood Mac.
After living in New York for 11 years, and then moving to London around the release of You & I ("We moved to London because things weren't happening in the US," they say), they're now back in America, but in Los Angeles.
"We love the weather, although there's a terrible drought here at the moment. Maybe it's all the ice bucket challenges?" says Allison, drolly.
n The Pierces release their fifth album Creation on September 1.