For years, Stu Lahn has been a familiar face at JASA’s Club 76 Older Adult Center on the Upper West Side, whether he’s calling bingo numbers, leading current events discussions or helping fellow members find discounted tickets to shows. Lahn has been involved with the center for 15 years. JASA, a nonprofit social services organization, operates older adult centers throughout New York City. “I tell everybody I went from being a workaholic to being a volunteer-aholic,” Lahn said.