The actual quality of a good show is something I measure in time. I mean, the really good ones, stick with me with tiny impressions on the long run.
For example, I remember exactly the type of chills and that particular feeling I got when I heard God Is an Astronaut‘s Fragile live, about 3 months ago. Hell, I still get those chills every time I listen to the song.

(Fragile by God Is an Astronaut)
photo by Richard Heeks
Nice track!
Oh, yes it is. From a nice nice album!