I think 8 rings is best. I often sit outside (without a mobile phone in hand) so if I hear my kitchen phone ring and make a mad dash up the stairs and in the back door, it's at least 4-6 rings. I HATE people who hang up after 4 rings. As a matter of fact, it happens so much that I often don't even bother to run to the phone if I'm outside.

One thing most folks probably don't know - and since I have two different phones (numbers) in my kitchen, and have used one phone to call the other - there is a 2 or 3 second delay between hearing the phone ring in your receiver and the actual phone you are calling ringing. In other words, when you think you let it ring 4 times, if you hang up immediately, it has only rung 3 times.