Maribeth, as you know, I too am a huge fan of checking with cast members after the show from the start of previews - it allows for a two way conversation. Just asking them if they have notes will allow them to get things off their chest, and also help you nip notes in the bud, and then I can turn around and give notes right away - but face to face and in a way that allows an artistic conversation to happen.
I am not a huge fan of posting run times . . . the issue is, that sometimes the run time is NOT the best measure of a show . . . the show could have been three minutes longer, but it could have been because of laughter, applause, etc . . . it could have been the same time as last night, but still felt rushed. Yes, the run time is a tool, but be careful about relying too much on it.
One of the tricks I use, especially on a long running show, I stop watching "the whole" show and instead pay attention to one performer, and watch their entire track. Or, I pay special attention to one scene more then another. Something to shake up my eye and my mind and keep things fresh - especially when I am watching form the house.
I find that during rehearsal, if you take down buzz words the director uses to direct a scene, you will find it helpful to reuse the exact words the director used.
Also, I find it helpful is to take the director for a walk, and ask them what they want an eye kept on, what they are worried about, what they would like to see grow, and what they want to make sure does not get out of hand.
I also am a huge fan to letting the actors admit their own mistake:
Me: "So, Scene 2 seemed a bit off tonight"
Actor: "I have no idea what you mean."
Me: "Your blocking seemed off, and there seemed to be a whole new intention on the first couple of lines - was something wrong?"
Actor: "Oh, no, I was trying something new."
Me: "Oh, well, I don't think it was completely successful, can we go back to the way we rehearsed it . . . (give a good reason, quote back some director's words here).
Getting the actor to admit there was a issue is half the battle some time.