In my area, zone 5, the perfect time to winter mulch is when the Christmas tree lots are in full swing. It's better to mulch after the ground has frozen because the goal is to keep the ground temperature constant rather than keeping it warm. And in the Thanksgiving to Christmas month there are plenty of evergreen boughs that have been trimmed from the bottom of trees that are just waiting for the taking. I also take all of my roping that comes down after Christmas and put that in my garden. The disadvantace of leaves is that they can compact and smother when they get wet. Another thing I do is collect straw bales that have been used as fall decoration. I about mid-November, I leave a note on the bale with my phone number offering to pick it up and organically recycle it. I don't shake the straw out but put it down in the "leaves" as it comes out of the bale. I the spring it will move to my vegetable garden to keep the weeds down between rows.