I seem to have my best luck in the evenings, and I am always prepared to skin 'em out, quarter them, and hang the quarters over a tree branch after dark. Last year it took until about 10:00 PM, working alone.
But, three years ago I killed one right at dusk. Mature cow. Could not find a blood trail because there wasn't one (muzzleloader, shoulder shot, no exit). Searched high and low for a few hours but couldn't find my elk, it had run a ways and not in the direction it started when I shot it so that threw me off.
Found it first thing the next morning, overnight temps. were around 25. It died out in the open, not under any trees, so heat loss was at a maximum, the night was clear. I thought the meat would be no good, but it was good, even the interior around the hip joint. All of it was good.
So, I wouldn't leave the skin on overnight intentionally, but if it happens, don't give up on the meat until you see for yourself whether it's still good.
