The hazards of being in rap-rock band 311 include a condition that, in musician vernacular, is known as “gig neck.” “We used to call it ‘the hinge,’ when you just headbang so hard that your nose almost goes to your chest every time,” 311 vocalist Nick Hexum explained recently. “That range of motion decreases a little bit as you get older, but it’s still a thing. First show of the tour, the back of your neck hurts a lot.”

Gig neck is a real concern when Hexum and his bandmates host their 311 Day marathons. Every two years, for one or two nights starting on March 11, aka 3-11, they stage epic concerts, usually in New Orleans. In 2014, they crammed a staggering 66 songs into a five-hour show at the Smoothie King Center.

311 Day returns to the Smoothie King Center on Friday and Saturday; both single-night ticket and two-night passes are still available. The plan, Hexum said, is to play entirely different sets each night, with no songs repeated. They’ll likely showcase nearly 80 unique songs across the two nights.

Breaking 311 Day into two nights “allows us to relax and stretch out more,” Hexum said. “It’s about pacing yourself, and having the peaks and valleys that a normal show does, but a lot more. A lot of it depends on where it falls on the calendar. Since this is a weekend, it was perfect to move it to two nights again.”

311 is both indefatigable and enduring. The band formed in Omaha, Nebraska, in the late 1980s, intermingling alternative rock, hip-hop and reggae. The current roster has been intact since 1992. So far, their collective resume includes 11 full-length studio albums, a couple of live albums recorded in New Orleans, a handful of alternative rock radio hits — including “Down,” “Come Original,” “Don’t Stay Home” and “All Mixed Up” — and many, many miles on the road.

The 311 Day tradition launched at the State Palace Theatre on Canal Street in 2000. It graduated to the Lakefront Arena and then the even larger Smoothie King Center. The party moved to Memphis in 2006 as New Orleans recovered from Hurricane Katrina and to Las Vegas in 2010 when a medical convention in New Orleans filled the city’s hotels. Otherwise, 311 Day has been in the Big Easy, where it inevitably includes nods to local music and culture.

Hexum is a fitness enthusiast — last month, he participated in a race to the top of the Empire State Building — so he’s already in good shape. But it’s crucial to play at least a couple of warmup shows before 311 Day.

“You can never recreate the full intensity of a show just in a rehearsal space,” he said. “You need the crowd there. You rock harder. Your body, your voice, the back of your neck — you can’t hit a 311 Day-length show cold.”

Fans travel to New Orleans from across the country to meet like-minded fans — and to possibly hear their favorite 311 obscurity finally performed live.

“This is for the hardest of the hardcore,” Hexum said. “The rarities, the B-sides, the deep cuts that they don’t get to hear that often — this is the time for that.”

Much to some fans’ surprise, and disappointment, the 2014 311 Day setlist omitted “Down,” “All Mixed Up” and “Come Original.”

“I’m surprised we didn’t do all three of those,” Hexum said. “Sometimes we just say, ‘These people have been to lots of shows, and they’ve heard those enough.’ We know they are the hardcore fans that will come to the shows when we come through town; our normal tour stops will have more of the familiar stuff. We want to make sure 311 Day is a unique experience.

“You can’t please everybody, but after being a band for more than a quarter-century, we’ve got a feel for what a situation requires and what songs would be a nice fit. The uniqueness is more the order of the day when it comes to 311 Day.”

They have occasionally rediscovered their own songs while preparing 311 Day surprises. “That’s happened, where we relearn something and think, ‘This is really working well live.’ The first time we played ‘Leaving Babylon’ after not playing it for 10 years, it became something that, on the following summer’s tour, we played nearly every night. It’s a nice way for us to refresh our familiarity. Some things do stick and go into rotation.”

At this point, they’ve deployed just about every song from their 11 studio albums. “We’ve played everything from the past few albums. I’d have to check the stats to see if there’s something that’s never been played. There would have to be certain songs from before people started keeping stats, the really old stuff.

“I can’t think of anything that has never been played that we could bust out on this 311 Day, but that’s the fun of doing the research.”

In 2014, they played three songs live for the first time: “How Long Has It Been,” “Make It Rough” and “Little Brother.” They also resurrected “Slinky,” which Hexum described as an “early, underground hit for us that we completely abandoned for a really long time. That was fun to bring back.”

Whatever they choose, drummer Chad Sexton will work especially hard on 311 Day, given the repetitive motion of thousands of drum strikes.

“If you’re being paid per note, he definitely would have more money coming than everybody else,” Hexum said. “He’s learned to relax his body so he’s not hurting himself. You have to learn how to relax in between hits. If you’re staying flexed the whole time, gritting your teeth, your jaw, that can really add up. You learn techniques to keep it healthy.”

And to avoid gig neck.

Follow Keith Spera on Twitter, @KeithSpera.