I don't know as I have only written them a couple of times with the same tone that is usual for me: professional and to the point. Both times I received a reply that was generic but relatively timely.
My own person philosophy on this though is that you have to be in the middle. That is, not too polite and not rude. This is because people tend to give to those who deserve receiving (who act as though things should be given to them). If you are overly polite, you seem desperate (and undeserving). If you are rude, people want to take away from you.
OK, I think too much (!!), but that's what comes to mind when you asked. :