Since rock’n’roll first became a business, conventional wisdom has dictated that if you don’t make it when you’re young, full of ideas and good-looking, you’re never going to make it. And, although many artists’ maturity makes a mockery of rock’s original “Hope I die before I get old” mantra, these acts, be they Chili Peppers, Quos, Albarns or Madonnas, tasted success at an early age and never wanted to do anything else.

In 2007, however, we may have witnessed a change in that paradigm. The stages of this weekend’s Reading and Leeds festivals may still be full of 20-year-olds, but there have been some interesting new kids appearing at the summer’s hardest-rocking events. Or, rather, old kids. A new generation of North American musicians is emerging into the mainstream – and they know that a touch of grey and a mortgage are, like ridicule, nothing to be scared of.

Making their main-stage debut at Reading and Leeds are the Shins. They formed as Flake in 1992, but their profile was raised considerably when their melancholic ballad New Slang featured prominently in 2004’s surprise hit movie Garden State. When their third studio album, Wincing the Night Away, arrived earlier this year, it reached No 2 in the US album charts. At 36, the Shins’ James Mercer was finally accepted as one of America’s finest songwriters.

“I remember having a conversation with my folks in 1999,” he recalls. “I said, ‘I’m going to work real hard and try to put together something I can stand next to and say, this is as good as I can do.’ If that didn’t work, I was going to go back to university. That turned into the first Shins album.”

Eight years later, Mercer and the rest of the Shins are on a global tour of festival main stages. The indie band from Albuquerque are officially stars. “I’m sort of glad I didn’t have this success when I was 25,” Mercer says. “I’ve grown a lot. I understand what it is I’m doing more than I did early on. My view of the songwriting process is a broader one now than when I was working on the first album.”

John Collins, of Vancouver’s New Pornographers, can identify with this. The band came together in 1997 after spending their twenties in local bands, going nowhere. Their third album of sophisticated, up-tempo pop, 2005’s Twin Cinema, was a critical success, topping the end-of-year poll for the prestigious American website Popmatters.com. They made their first appearance at Glastonbury this summer, and they now have a fourth album out, Challengers, which seems destined to be their biggest so far.

“Until things start to break down physically and mentally, you tend to get more limber and fluid as you get older,” Collins says. “Whatever the musical part of the brain is, it’s more developed now. I feel like I can pick up an instrument I’ve never played before – for instance, the mandolin. I played that on our last record. It was, well, easy.”

“You always keep getting better,” agrees Craig Finn, the bespectacled and balding front man of Brooklyn’s the Hold Steady, the band who stole the show at Glastonbury. “Once you figure out what you’re good at and what you’re not good at, you keep working at what you’re good at.”

Having played in the little-known indie band Lifter Puller for seven years, Finn formed the Hold Steady three years ago witha bunch of like-minded friends, with the dual objectives of drinking beer and writing songs like Bruce Springsteen. Tonight, they are headlining the Carling stage at Reading.

“One of the things with the Hold Steady was that we were able to take a contrary position to what was going on, which was basically syncopated dance music,” Finn explains. “Nobody was doing sloppy rock with big guitars and good lyrics. I said, ‘We could do that.’ Sure enough, a lot of people were interested in hearing that. Being a little older did affect us in the big-picture way. I think we were more grateful for it than we would be if we were 21.”

Perhaps the sudden rise of mature bands isn’t coincidental. You don’t have to search hard to find older music fans unimpressed by the current clutch of hype acts. At the same time, turning 30 doesn’t mean that listeners can suddenly cope only with Simply Red or Coldplay. For the first time in years, thirtysomething fans can go out to see new bands play small and midsized venues without feeling they are crashing someone else’s party.

“We’ve found a lot of our fans are people very similar to us,” Finn says. “These are the guys I graduated college with, with three kids and a mortgage. They need a baby-sitter to go to the shows. It’s really exciting to see. People feel like they’re being ignored by the industry. They try to get into new bands and think, ‘This isn’t something I should be listening to at my age.’ I hope what we’re doing is timeless and classic, in the sense that we’re not tied to one particular trend.”

A willingness to stand apart from 2007’s trend for jerky, dance-friendly postpunk is a unifying musical theme that links this older generation of breakthrough artists. “I’ve been telling young bands I meet for the past 10 years to check out Gang of Four and Wire,” Collins points out. “They’re the greats. But as to where that fits into what we do, it’s several layers underneath. It’s not something new that we’ve discovered and that we want to bring to people because we feel like nobody has heard it before. It would be bizarre just to be emulating the stuff we love. Trying to become the next dance-punk stars seems kind of irrelevant.”

It could turn out that 2007’s most unlikely star is also its oldest. When the American bluesman Seasick Steve makes his first appearance at the Reading festival tonight, it will be the culmination of a remarkable journey. After decades of playing in abject anonymity in clubs and on streets, followed by a near-fatal heart attack, a brief buzz and a show-stopping appearance on Jools Holland’s new-year Hootenanny, he has suddenly become rock’s favourite senior citizen.

“I didn’t think anyone was interested in primitive music,” smiles Seasick Steve, after politely refusing to divulge his age. “But I started playing in front of punk-rock kids, and they were going crazy. For years, when I spoke to kids about blues, they’d just yawn. They thought it was middle-aged men with ponytails.”

Rock’n’roll may still be a young man’s game, but Steve has proved that it’s never too late to launch a musical career. “My peak is now,” he announces with a booming laugh. “I was happy playing in my front room. Now, everywhere I play is sold out. I didn’t dream about doing this. My dream was being alive.”

New Pornographers’ Challengers is out now on Matador

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