I have always recommended changing the sheet cut blade once a month when using the sheetcut frequently. The machine ships with a pack of 25 blades. After changing the blade each month for two years, buy a pack of replacements (25 pack) for $10.00 to last another 2 years.
Every bit of stress and strain you can eliminate from the scan motor will increase its lifespan.
Small price to pay to help prevent a $400 motor replacement, or more.