We start our winter workouts on Dec. 1st each year. Our conditioning starts the week we get back from Christmas break in January, and our lifting/plyos program begins around the same time.
I don't like to get started too early, as I've seen many teams that do burn out at the end of the season. Our players play in a wood bat fall league (18 games), so the ones that play in that league just finished their final game on October 23rd.