I check every round that goes through my press to see if the powder "looks" right in the case from what I know the load to be previously.
Every (Nth) round gets weighed anyways, but if one looks high or low it gets checked.
The Lee Auto Disk system is fantastic. The adjustable charge bar also works swimmingly.
Power manufacturers can have something like a 16% variance in VMR and still be within tolerance, so the charge bar is a wonderful tool.
You just literally "dial in" your charge weight and then go to it.