https://www.showclix.com/event/TheLateShowwithStephenColb604314 recommends "you get in line no later than 15 minutes prior to 3:15pm". https://en.wikipedia.org/wiki/Late_Show_with_David_Letterman says that that the show is "recorded Monday through Wednesdays at 4:30 p.m., and Thursdays at 3:30 p.m. and 6:00 p.m. Eastern Time. The second Thursday episode usually aired on Friday of that week.
So is the 3:15pm suggestion for M-W or is it also valid for both Thursday filmings as well?
And even if 3:15pm is the latest you'll be allowed in line is it reasonable to get in line at 3:15pm and still get tickets or should you expect to be in line a lot earlier than that?