I think it feels most right when temps get below 70, which is coming soon, in about a week or so, but I don't put too fine a point on it.
I have some trousers that work best with ankle boots (worn long) and some transition-season light sweaters or long-sleeved blouses, so that doesn't scream "changing to boots," so I'll am wearing them before I break out the opaque black tights.

My boots go on when it rains. I love to wear my closed toe shoes on nice fall days though. There's a short window of opportunity here where I can wear my shoes without carrying them separately in a bag due to snow! :-). I get to wear my boots daily between November and the end of April without a break.