I presume that you mean with a arrow. A good hit and I see him drop 15 minutes, if I don't see him drop at least 30 minutes. A bad hit, it depends on where I think that the arrow went. Any where from 45 minutes to a hour and a half. Then depending on what I see in the blood trail I may wait a little longer.
Any time I shoot a deer, I'm excited, and GLAD I am. I have found a system that seems to work well for me. As soon as the deer has gone out of sight, I check where that spot was, then check the spot he was when I shot, set them both in my mind and look at my watch. I wait 10 minutes, by my watch, religeously.
Of course, if the deer falls in place, or falls in sight (most of the time), I use a different procedure. I spend the 10 mins, getting my gear together (if I was in a stand), reloading my rifle, and taking OFF layers, if I was in a cold weather stand (after all, I'll soon be gutting and dragging). The 10 mins seems to work very well in calming my nerves, and getting me prepared to follow the blood trail.
I follow the trail slowly watching both the blood at foot and the area ahead for the deer, either dead or lying head up. The last time the trail ended at a deer, lying head up was '02 and he needed another whack as he tried to get to his feet, about 35 yds away.
I think 10 minutes works for any gun shot deer, unless you also have a gut shot deer. And then, my friend, you have a problem.
Since I'm only dealing with a gun shot...I believe in the "keep him moving theory" for a bad shot. I figure if the wound is bad enough to be fatal he won't go far...bump him up, wait a bit and let him run a bit... get his heart pumping out blood...bump him up again...until dark. Then come back in the morning pick up the trail and repeat.
When it comes to scent, there are basically two types; those that attract and those that mask. I've tried both on many occasions. There are lots and lots of "doe in heat" scents, designed to attract a big buck into range. I've also used a "cow in heat" scent while elk hunting.
Another scent would almost be better named as a "coverup smell". The main goal is to cover up human odor or mask it. Though I don't believe you can ever totally eliminate all human...