INDEPENDENCE, Ohio — There haven’t been any championship banners hoisted into Boston’s hallowed rafters since 2008. LeBron James won’t let go of the rope. Cleveland’s star has bounced the Celtics from the playoffs four times in the past seven years, and James carries a six-game postseason winning streak at Boston into this year’s Eastern Conference finals, which open Sunday at TD Garden. As a member of both the Miami Heat and Cavaliers, James — whose success against Boston did a 180-degree turn with a mesmerizing Game 6 performance in 2012 — has made the Celtics green(er) with envy. But while the 33-year-old has the utmost respect for the NBA’s most decorated franchise, James’ admiration hasn’t stopped him from standing in the way of Boston stuffing more Larry O’Brien trophies into its crowded case. And if he beats the Celtics again and advances to his eighth straight NBA Finals, James would join a club currently exclusive to Boston players with legendary status. Only Bill Russell (10), Sam Jones (9), Tommy Heinsohn (9) and Frank Ramsey (8) have played in more consecutive Finals than James, who said he hasn’t reflected on the possibility of admission to their group. “I do know that this is my eighth straight conference finals and I have an opportunity to play for a championship if I’m able to be successful in this conference finals, so I don’t take that for granted,” James said Friday.