Turned into an interesting thread!
My father spoke to me on shooting ducks "if you think you can get him, don't shoot... Wait till you know you can get him." I believe it applies even moreso to turkeys, as they are a far easier target when in range.
It occurred to me this season, that as I am watching a bird come in range, there is that point, in which my brain clicks "he is in range now, and I am comfortable with shooting him." If he is coming in closer with confidence, I let him continue come (to about 15 yards)... My comfort range is about 35 yards, but I have and will take them at 40...
But that bird that starts to get nervous, cause he does not see a hen, or starts to sense something is wrong... I shoot him on the spot (once in my comfort zoen). A nervous bird usually already has his head up...