Wouldnt this all depend on time of year, weather conditions, etc? If it were me, and I REALLY REALLY needed to make the next flight, i'd plan to get there a day early. Having had severe thunderstorms and snowstorms push me from the last flight of the day to the first flight of the next day, and having had all flights into a certain city cancelled even when i was originally booked to fly early in the morning, i'd be extra conservative. Worst case you get a cheap hotel room and/or chill in a positioning city for a while.