The phrase "avid attendee" is correct and usable in written English.
It can be used to describe someone who is enthusiastic and regularly participates in events, meetings, or gatherings.
Example: "As an avid attendee of the annual conference, she never misses a chance to network and learn from industry leaders."
Alternatives: "enthusiastic participant" or "dedicated visitor.".
He was an instant convert and thenceforth an avid attendee, a member of the earliest cadre of Dead freaks who bore witness to the band's metamorphosis from a mere blues-and-dance band into a full-bore improvisational psychedelic experiment — what he called "primal Dead".
Rose Qassab, 22, an Iraqi citizen who graduated from the Canadian college CAN-Q in Qatar last June with a degree in business administration, is another avid attendee who has convinced managers at her workplace, HSBC, to join her at recent debates.
In exchange for use of my spare bedroom, he offers his services as my tour guide to a little-known event that is nevertheless one of the biggest happenings annually in the pizza world: the three-day International Pizza Expo, which this year will draw 8,000 avid attendees.
An elementary school teacher, avid lecture attendee and world traveler, she was enthralled by the peaceful, warm summer days in her cherished Easthampton hideaway.
Together with his beloved wife, Janet, Dan was an avid theater attendee and enriched our endeavors with his breadth of experience, both professional and personal.
An avid theater and museum attendee, Jackie instilled the importance of art in her two sons.
I want to buy real cows!" Still, Stewart seemed, like most of the attendees, to be an avid networker.
Among the attendees was a representative of a major casino company in Las Vegas — Mr. Takahashi is an avid gambler and a frequent visitor to the city — and Stanton D. Anderson, a longtime Republican activist and a consultant to the American Bible Society.
