Free: Contests & Raffles.
If I find him, I'm at the very least field dressing him, but I'm probably going to quarter/bone it and stash what I can't pack out. Once it's dark, it's dark, and if I have an animal on the ground, I don't really care how late it is since I'd be packing the next day anyway. Carry a good headlamp, a backup headlamp, and some batteries and get to work!
Time of day really has no impact. Meat's got to cool no matter what.
I guess I don't understand anyone would consider not immediately field dressing (boneless/gutless, quarters/gutless, just gutting, whatever) any big game animal upon shooting/dropping it (or finding it after tracking)?