All day is very hard and wears you out- but I do it every year on key days.
Though I am the traditional wool preference guy, I have found that fleece is less bulky and lighter in wt. allowing better shooting than wool. So, here in the midwest. . .
Light merino wool base layer (and an extra if really cold out), wool sweater, insulated fleece vest, windstop fleece outer jacket (Love the predator brand for quiet and fleece wt!). Bottoms are similar with wool pants instead of fleece. HOWEVER, I also carry in an extremely XXL fleece pants with elastic band. They are extremely light, but are awesome to pull on over all my other stuff- almost like a Heater Suit. They go up to my chest. It saves the day!
Chemical handwarmers, including one in a small bag or sock tied to hang from neck against my chest- makes a wonderful little furnace! I then sit with the jacket bloused away from my chest to provide dead air space.
Also a strong believer in extra hats and covering your neck.
Big pack boots. . . a thermos of hot tea. . .snacks. And if the day gets long, I just get down and take a nap next to the tree. Would rather be there than leave!
Good for the day
My 2c
Dan