Photo: Elde StewartCrosby, Stills & Nash must be having a very, very, very fine time on the road this summer.  The folk-rock legends have extended their expansive U.S. tour, which kicked off in early June and originally was mapped out through the end of September, well into October.  The Rock and Roll Hall of Famers have tacked on a four-night stand at New York City's Beacon Theatre that includes shows scheduled for October 16, 17, 19 and 20.

With CSN's three members either over or nearing 70, you'd think they might be ready to shy away from such a lengthy trek, but Graham Nash says that just isn't the case.

"It's 78 shows.  So what?  That's what we do," Nash declared during a recent interview with ABC News Radio.  "You know, I'm very fond of saying, 'If I'd have been a plumber for 50 years, I'd be a great plumber.'  It's a muscle that you use…We write from our experience of life [and we] want to deliver it to the audience as purely as possible."

Those going to see CSN in concert will, of course, get to hear plenty of the group's classic songs, but they also will be treated to quite a few lesser known gems from various periods of David Crosby's, Stephen Stills' and Nash's long careers.

"Yeah, we need to play 'Our House.'  We need to play 'Teach [Your Children].'  We need 'Guinevere.'  We need 'Southern Cross,'" notes Nash.  "[But] our audience always realizes that anything might happen at our shows.  A song that we haven't done in the last 30, 40 years, or a song that we wrote this morning -- our audience expects craziness from us and they get it."

Fans can get a good idea of the kind of show Crosby, Stills & Nash have been delivering during the current trek by checking out the group's new concert DVD/CD set, CSN 2012, which documents a concert the band played in San Luis Obispo, California, this past April.  Among the interesting performances featured are a brand-new Crosby composition called "Radio," a cover of Bob Dylan's "Girl from the North Country," Nash's 1971 anti-war tune "Military Madness" and Stills songs from his time with The Buffalo Springfield and Manassas.

Nash told ABC News Radio that CSN 2012 serendipitously catches the trio and their backing group in top form.

"It's unusual for the three of us to all be as strong as each other on the same night, and it's unusual for the band to be spectacular on the same night," he maintained.  "So, when you put those two together, it was a fabulous, fabulous concert."

The singer also said that when he watches the video, he gets a sense of how the positive aspects of his relationship with his band mates has endured and thrived.

"To me, it's very obvious that we wanna be there, and it's very obvious that we love each other," he insists.  "In spite of all the madness that has gone on in this band, we're still, dear, dear friends."

CSN's next show takes place Wednesday in Lincoln, Nebraska.  Visit CrosbyStillsNash.com to check out all of the band's upcoming tour dates.

Copyright 2012 ABC News Radio