Richard Thomas, star of “The Waltons,” knew it wouldn’t be easy to prove to audiences that he could play characters other than John-Boy Walton once his gig was up. “I figured, I’d been in the show for five years,” the actor exclusively told Page Six in a new interview. “It was going to take at least five years to sort of do enough work to start to balance the scales.” Thomas, who left the hit ’70s TV series after five seasons, was quick to stress that he “adored” the show. Richard Thomas, star of “The Waltons,” exclusively spoke to Page Six about his career journey in a new interview. Page Six The actor (pictured in the middle, standing) starred as John-Boy Walton in the hit 1970s TV series “The Waltons.” ©CBS/Courtesy Everett Collection “I have nothing but only incredible gratitude, affection and fond memories. It was a wonderful piece of television for its time,” he gushed, noting that the series aired when there were only three broadcast networks and when TV audiences were huge.…