“That thing belongs in a museum,” remarks mercenary leader Barney Ross (Sylvester Stallone) upon glimpsing an aging plane the shadowy CIA agent “Mr. Church” (Bruce Willis) has presented to the eponymous characters near the end of The Expendables 2.

“We all do,” fellow mercenary Trench (Arnold Schwarzenegger) pithily replies.

It’s a case of saving the film’s best joke — which isn’t saying much — for last, but there’s more than a kernel of truth to the remark. Ah-nold and Sly are both sexagenarians, and Willis isn’t far behind. But this trio’s advancing years didn’t stop The Expendables from racking up $300 million worldwide two years ago, and evidently the chance for them to recall their action hero heyday once again was too tempting to pass up.

The mayhem kicks off here with the team coming to Trench’s aid, helping him rescue — in typically bloody fashion — a kidnapped Chinese billionaire in Asia. They’ve scarcely finished this mission, though, before Church shows up to offer them another: recovering a mysterious package from the fictional Eastern European country of Gazak.

The returning Expendables — Lee Christmas (Jason Statham), Yin Yang (Jet Li), Gunner Jensen (Dolph Lundgren), Toll Road (Randy Couture) and Hale Caesar (Terry Crews) — are joined by a couple of newcomers: Billy “the Kid” Timmons (Liam Hemsworth), an ex-army sniper who’s not sure this is the life for him; and Maggie (Yu Nan), a loaner from the CIA who the team isn’t sure they want tagging along since Church says he’ll hold them responsible “if she gets a hangnail.”

Before they can complete the mission, however, the team’s intercepted by Jean Vilain (Jean-Claude Van Damme), a brutal rival mercenary on the same trail. A confrontation ensues, during which Vilain and his goons murder Billy and take off, giving the Expendables a new objective: “Find ’em. Track ’em. Kill ’em.”

And that’s pretty much what happens, with Trench, Church and Booker (Chuck Norris), a retired military operative, popping up at key points to lend a hand.

For many fans, that will probably be enough. The violence is sometimes laughably unrealistic, but there’s no shortage of digital blood, guts and gore. When the film tries to be anything other than an orgy of destruction, though, it fares poorly, as when Barney laments the cosmic injustice of Billy’s death.

“Why is it the one who wants to live the most, who deserves to live the most, dies, and the ones who deserve to die, live?” he asks. “Why is that?”

Stallone waxing philosophical here offers much unintentional mirth, far more than when the film tries to be funny and is instead moronic. During some downtime, the gang discuss what they’d choose as their last meal.

“I could go for some Chinese,” says Gunner, leering at Maggie, to which Barney replies: “You’re gonna starve.”

But the film’s juvenile sense of humour can’t mask the fact its cast is aging (although Stallone’s face suggests he’s made a valiant effort). There’s plenty of shooting and blowing stuff up, but not much physical combat, and only Van Damme appears at all agile. To borrow a line from another action franchise, the rest generally seem like they’re getting “too old for this shit.”

Indeed, two decades or so ago, Stallone, Schwarzenegger and Willis sharing the screen would’ve been a formidable combination, at least in star power if not acting talent. But today, it speaks more to the fact none of them have the wattage to carry a film such as this on their own anymore.

As this vanity project reveals, however, they’re not prepared to fade quietly. Schwarzenegger’s museum quip might seem wryly self-deprecating, but it also suggests Stallone and co. believe they’re deserving of posterity.

It remains to be seen whether their earlier work will stand the test of time. But The Expendables 2 doesn’t belong in a museum: there’s nothing here worth preserving.