I age my ducks and geese as well as venison. How long is all dependant upon weather. I gut everything and hang, ducks and geese about 4-5 days and venison up to 2 weeks if I can get temperatures about 50 degrees. I leave the hide on deer unless it is warm when it's shot, then I skin right away to start the cooling. If temps are reasonable I will leave the hide on, because it reduced the amount of moisture that is lost during hanging. All of my deer hunting is done on our property, so I usually have them hanging within the hour after kill. Key is getting body temperature down as fast as possible, then you can hang without worry, even in temps in the 70's. Makes the meat much more tender and flavorful, not gamey. I wouldn't bother with pheasant or quail, because they are generally tender anyway. Won't do any good for hogs either.
I read that someone recommended using salt. Not a good idea, because it not only pulls blood, but moisture from meat. That will make it tough. Most of the blood will come out anyway, all you are doing is removing valuable juice from meat. Venison/game is lean enough without it being dry too. Also never cut meat when it's still warm from body temperature, because it makes meat very tough. You can quarter if necessary, but don't cut across grain. At a minimum deer should be hung until cooled before processing.
If you've ever had an aged steak you know what a difference that can make, same goes for game. I just built a pole barn and going to make a walkin cooler so I can age my meat even longer and in any weather, I will try to get to 28 days if possible...