Unless it's changed recently, last time I was in AK and there was just one RoL show during the night, standby was full 60 min prior to showtime.
With just one show people pack in and pack in early. I'd recommend getting there around 90+ min early. The show has mixed reviews (I strongly dislike it), but I don't think it's popularity has died down much because there's still a ton of people that have yet to see it. It's a lot easier to attend the second show when they do two showings