How Soon is Too Soon to Turn on the Heat in Your House? [POLL]

So I came home yesterday after watching some football, and I noticed the smell.  You know -- the smell of the furnace that hasn't been used for months.  Yes, it was chilly, but my wife decided to turn the heat on!  I looked at her like, "No way." It's only September!  There is no way we should turn the heat on.  I bet that if I went door to door down my street, we would be the only house to have the heat on.  So I ask you, my level-headed listeners...