How long should you wait for an answer?

Answer 1

if you are waiting for someone, wait for about an hour, then leave and move on

I would say, wait only about twenty to thirty minutes for a friend. An hour is too much of an imposition to you.

20mins max! its the 21st century we all have cell phones now

Lateness is just another form of rudeness [with the exception of an emergency ]. 15 minutes, and they can call with an apology and an explanation when it is convenient for them, obviously.

Answer 2

In some research and lectures, I heared about 8 seconds is long enough. This is enough thinking time to develop an answer, and if one is not reached by then it is unlikely, unless further prompting and questions are asked.