With only three label releases under its belt and a captive audience, it might seem like Nickel Creek is just getting started. But, actually, it's been 18 years since the Thile and Watkins families formed the bluegrass trio in San Diego that would eventually evolve into popular band on the Triple A/Americana circuit.

And now it's time for a break.

Nickel Creek is on a last waltz through America before going on an indefinite hiatus. It comes before the trio -- formed when members Sara Watkins (fiddle, vocals) and Chris Thile (mandolin) were only 8 and Sean Watkins (guitar) was 12 -- ever had a chance to hit a downslide.

"There's a danger of reaching that point," says Sean, "and we never wanted to get there. It's been 18 years since we've been a band, and it worked out contractually, and everything seems to dictate that's what we should do. It's not like we're not getting along. We just have a lot of other things we want to do."

The impetus, he says, was the pressure to make a new record, and "we didn't have the songs, and we were thinking about how much the last one took out of us."

The band's first record for Sugar Hill, a self-titled release in 2000, was a critical and commercial success that established Nickel Creek as a progressive bluegrass force while going gold and garnering two Grammy nominations.

The timing was perfect, coming in the wake of "O Brother Where Art Thou?," with "O Brother" soundtrack star Alison Krauss producing.

"A lot of people bought the first record because they were into 'O Brother,' " Sean says. "We kind of rode on the coattails of that."

With the trio coming of age in 2002, "This Side" was more of an indie rock statement, even including a cover of a Pavement song. Nickel Creek's final release, at least for now, was 2005's "Why Should the Fire Die?," dubbed as the bluegrass-folk answer to Radiohead's "Kid A" for its embrace of experimental pop.

Although the band is going to draw the line there, a lot more music is on the way from the individual members. Sean is set to appear on Sara's first solo record, which is being produced by Led Zeppelin's John Paul Jones.

Sean, who has already issued three solo records, has a few different projects in the works. The first is a record due in the spring with fellow San Diegoan Jon Foreman of alt-rock band Switchfoot called "The Real SeanJon."

"It's a little bit closer to what he does than what I do," Sean says. "It's more in the rock vein, but with some folky songs on it."

The second one is another Mutual Admiration Society supergroup project with Glen Phillips (Toad the Wet Sprocket), Sara, Benmont Tench (Heartbreakers), and two members of Elvis Costello's Imposters. "The guys are so good; it's pretty much a live record," he says.

First, though, he and his partners have to finish this tour, which will culminate in a final performance in L.A. that will be filmed for a live DVD.

"It's been really fun," Sean says. "We're all in good spirits, and every night there is something new -- it's not just playing the old songs one more time."