Brilliant venues, from Vegas to Biker Bars, discovered that clocks are bad business, but I always detested the 'look at your watch onstage' maneuver.
Yes, you'd get a ration of shit if you stayed on too long but I always felt it made the audience feel like you must have something better to do and couldn't wait to get out of there.
Nobody cares if you look down for a second and fiddle with a knob.
45-minute set? No problem. During my intro, I'd ask a backstage guy for the time. 9:48? I was done by 10:33 on the nose.
I never wore a watch. Managers and crew asked me how the fuck I did that.
I told them that the Jeopardy theme is exactly 30 seconds long (it is, btw!).
Then I told them that for, let's say a 45-minute set, I'd hum the Jeopardy theme in my head 90 times while I was onstage.
Then I'd walk away.