IMHO, they only work at the right time of the rut. From what I've seen, it will actually scare them away if used at the wrong time of the rut. Deer are instinctual and if they smell it at the wrong time, they will spook and leave the area. At least, this is what I have experienced doing some rudimentary testing of the stuff. From what I can tell, it looks like it is most effective in the last few days before peak rut hits and the first few days after the rut starts to tail off.

Here's how I did my testing:
I took one of those bathroom automatic sprayers (they spray freshener every 9, 18, or 36 minutes) and painted it using some home-made camo patterns. I set it for spraying every 36 minutes and put a spray bottle full of Code Blue estrous spray in it. I also set up a game camera on the same tree. I left this rig out for about 6 weeks over a known scrape area (2 weeks before rut, est. 2 weeks during rut, and 2 weeks after rut would normally end in central GA) where I hunt and checked it each week to make sure the spray bottle didn't run out. Before the rut, scrape activity was minimal and I only had a few pictures... mostly does. During rut, I filled up the memory card in the camera and I had a 60-40% mix of bucks to does. Post rut, I had about the same mix of bucks to does (60-40) for the first few days, then it tapered off quickly after about 3-4 days after the rut had ended (my estimate), then back to the typical "just a few pictures".

So, I will use scents, but only starting a few days before, during, and a few days after the rut.

I could be WAAY off base on how I tested them, but, I'm not a scientist, biologist, or game expert. Just a simple computer geek that likes to experiment and see what works in my area.

Cheers!
MadOtis