It throws me a little if somone picks up the phone straight away so I will leave it ring twice before answering. If I am phoning someone else, I usually hang up after 10 rings. I may dial for longer but I think it would need one of the following:

1. I know the person I'm calling has trouble getting to or hearing the phone.

2. The call is important and I feel the person the other end is choosing not to answer. I've done the same myself from the other side as well as the answerphone trick where you wait to hear who speaks before deciding to answer.

3. I'm trying to contact something like a local authority. Similar in a way to my #2 but I feel some of the sods just like to keep people waiting on principle.