Example: Okay, say that you are sitting down at a table at a place that is relatively busy. You are just about to get ready to head off to your next destination. A person approaches you by the side and asks if you could look after their stuff for a second. They seem like they are in a hurry, so you say yes. 

How long do you expect to be waiting for? 

However long it takes to look over the stuff. So sit down and listen.

Would you wait for thirty minutes? Or would you have expected them to return much earlier?

In my country, with our laid-back culture... it would not be something fast.

How long would you be expecting/willing to wait for? 

You never said anything about leaving.

The meaning of the phrase depends on the situation, but in the situation you're describing I'd expect something like 5-15 minutes.

Take their stuff and move to your destination leave a note where u are going

Edit 5 mins tops

In the example I stated that before the person approached you, you were just about to get ready to leave. So the option to leave once a certain amount of time expires is heavily implied - especially if you grow tired of waiting.

You NEVER answered my question. See - two can play at that game.

You never said anything about the other person just leaving. If someone asks me to look over something real quick I expect them to have it with them. And if they don't, I ask them what it is and why they think I should have an opinion about it. I don't even know them.