Darren Prince of Prince Marketing Group tells TMZ ... the holidays really are the most wonderful time of the year for Chevy -- he just wrapped 2 sold-out Q&A screenings of the National Lampoon classic at Foxwoods Resort Casino in CT, and he has a 2-day Comic-Con appearance in Pittsburgh this weekend.

What's more, the actor's got another 'Christmas Vacation' screening booked in Atlantic City next weekend, followed by another in Michigan. Yeah, the guy's gonna need a real vacay come Christmas Day.

We're told his team refers to December as Chevy's Super Bowl month, no doubt because of the massive popularity surrounding the movie 30 years after its release.

Darren says he's seen a resurgence of fans in recent years, making it clear a whole new generation is being introduced to the film.

Patrick Ganino, who runs Chevy's social media and travels with him, tells us Chevy really enjoys all the stories he gets to hear ... and it's now clear to him how the movie helps a lot of people through tough times, especially around the holidays.

As we reported, Chevy teamed up with Raising Cane's at the end of November ... channeling his inner Clark Griswold by lighting up an impressive Christmas display out front of a Chicago location.