IMO, using decoys often does more harm than good, often reducing your chances of killing. I'm saying this not only because decoys often repel rather than attract turkeys, but also because hunters are often unknowingly seen by distant turkeys when the hunters are placing their decoys (and/or retrieving those decoys).
I sometimes use a "sitting" hen decoy, which is typically not visible to any turkeys until they're already well inside the kill zone (ideally, under 30 yds). Once seen, again, the Tom would typically already be under 30 yds when he sees it, i.e. I "called" him in, the decoy had no role in getting him there. But once he sees it, he may then stick his head up higher, go to it, and/or "hang around" (in range) longer, offering more opportunities for a good head shot. I mainly do this when I'm calling up a bird for another hunter; usually do not use a decoy when I'm hunting by myself.
Just to emphasize, I'm not using this decoy to "bring in" a turkey, as it's my belief decoys "repel" as much or more as they "attract". Add to this repulsion the risk of being seen or heard placing/retrieving, and the decoy(s) become a net liability. Add to that, having to carrying them. The sitting hen decoy's purpose is to provide more head-shooting opportunity on a bird ALREADY in the kill zone. This extra opportunity can be very beneficial for a young or inexperienced hunter, but may be of little value to a more experienced turkey hunter.
The disadvantage of even a "sitting" hen decoy is that should a bird see it while out-of-range, they will often come no closer. This "repulsion" is even more often with standing/feeding, jake, and full-strut decoys. Hence, the decoy cost you the kill.
When I use a "sitting" hen decoy, I've learned to typically "hide" it, so that it is less likely to be seen until the bird is already in the kill zone. For whatever reason, the "sitting" hen decoy less often repels a bird that suddenly sees it point-blank, whereby a more regular "standing" decoy often causes turkeys to "lock up", come no closer, then go away.
To reduce the chance of being seen (or heard!) placing a decoy, it should be placed at least 30 minutes before 1st light. Even that sometimes backfires when nearby roosting birds may hear you accidentally make an unnatural noise, often causing them to go any direction but yours when they leave the roost.
I'll just say turkey decoys have been so successfully marketed that some want them outlawed, they so believe that marketing. What's not seen in the "marketing" videos (as well as hunters first-hand seeing them work), are all those times decoys cost the hunter a bird. That is very difficult to measure because you don't "see" it.
For every tale of a decoy working like a magnet, there are the untold, often unknown, times the use of decoys repelled multiple birds, before working "as advertised".
