Erm, there are some days that even my fire department frequency goes without traffic for 3-4 hours or more. When I worked security, there were some nights I didn't use the radio at all...
Grab one of the ubiquitous VOX recording wav programs. Patch your scanner to your line-in point on your computer, leave it running overnight (or longer, if you have enough radios to do that) on the frequency/ies, and see what you get... you won't know WHEN it came across, but you'll know if the frequency has traffic or not.
If you're monitoring trunk(s) using a tapped scanner, you could use something like T4Win to log if the talkgroup has received any hits and when. I'd love to see something like T4Win (at least the tracking portion), but for conventional frequencies. Maybe it's out there, or maybe someone with programming experience just needs the bug put in them.
