I tend to give the deer more credit than some. But I have watched a buck lie still while a hunter passed within yards , and I have seen that same buck bolt from his bed because some one slammed a truck door out on the road.
When I look back at the bucks I did not kill the number one reason was the wind. It now has become the number one factor in what stand I will hunt or if I will hunt.
As for age ,a buck has a short learning curve and if they make past 2.5 years old they pretty much have a masters degree in survival.
They might question what they see,and even what they hear but if they get a whiff of you the game is over and and they will melt away without many ever knowing they were there.