The device's daily duty cycle is the manufacturer’s recommended daily limit, or the number of scans you can do each day without causing undue wear and tear on the machine. This is usually a relatively large number. For a scanner with a 1,000-page daily duty cycle, you would have to load its 20-page ADF more than 50 times in a day to exceed the volume limit. That’s a lot of scanning. I've heard it suggested that you need to stay under the volume limit to keep from voiding the scanner's warranty. However, I haven't found that information in any warranty yet, and that's not for lack of trying. Also, I've never heard of a warranty being voided for far exceeding the duty cycle. If you occasionally go above and beyond, I wouldn't be too concerned about repercussions. It's more likely that the ADF, the scan speed, or other aspects of the scanner will keep you from ever going all that far above and beyond the rating.