Assuming you aren't working in the pro world and dealing with deadlines and customer expectations, how long you spend for a shot depends on your working style and what you're looking to accomplish.
If you're looking the right light to happen or some other condition you aren't controlling, there is not much else that can be done.
OTH a bit of fast work training can be helpful for those situations where you must deal with rapidly changing conditions to get the shot you're after.

If you have an impatient observer, you can always tell them you'd like to explore the setting further, and send them up the road and arrange to catch up later.