I apply this rule to all days afield.
What I mean is, when in Rome.....
If the bucks are starting to get aggressive, you will notice it. At least we do up here in Michigan. I have witnessed a small six point snort wheeze at a spiker as early as the first week of archery season (starts Oct. 1st).
Can I say that this is the same year in - year out, heck no. But when I see this type of activity going on, you can bet I am going to start bringing the hardware to the woods to imitate them.
I seem to have good success bringing in early October bucks with a few ticks of the antlers mixed with a few tending type grunts. When the activity starts to rev up, then so to does my aggressiveness with the calls. Might just be for a night or two (guessing weather related), or may just be the very beginning of the pre rut. I don't really know, much less care. I just see it, and try to imitate it.
Hunting the Michigan Thumbs agricultural mecca...farm country bucks taste the best.