I pretty much only record during high-risk times, which around here (North Carolina) means rainy days. In some other places, hot days and early season snowfall are ripe for bad driving, so I'd record that too. I've also done a few recordings just for fun on recreational rides.

I got a camera after an accident last summer (which was followed up by some absolute ridiculousness from law enforcement). A recording of the incident would have been very helpful in making my case, but would not have eliminated the awfulness of bruised ribs. So, recording comes down to a risk assessment; if conditions make it more likely that I'll encounter funny business, I'll record; otherwise, it's not worth the hassle.