how long do you let SP make you wait before you leave?

[Robert Mugabe]

Depends on my mood. How disenchanted I am with the implied "Sorry. Can't talk right now. I've got somebody's balls slapping against my chin"

 

[belissimo]

Upwards of 30 mins if the provider is well known/good rep and there is communication. 10 mins if the provider is more of an unknown.

 

[barnacler]

ANY mention whatsoever of another client being the reason and I'm gone.

And the corollary of that is if I am running late, I always tell them to start the clock for me at my appointment time.