When we've shown up early for a PS a few times (by 45 minutes or so), we've been worked into the current PS schedule, and have only waited around 5 minutes. On the other hand, when I think about it, we've moved from a later, more popular time to an earlier, less popular time so they may have been happy to fill the tables up earlier. I suppose if you had a PS for 8:45 and showed up at 6:30 p.m. instead, there might be more of an issue.