We were impressed by the Landworks Wood Chipper Shredder Electric Light Duty 17:1 Reduction 15-Amp 1800 Watts 120VAC Dual Edge Blades for Lawn and Garden Use or Fire Prevention Building a Firebreak.
Depending on the conditions that your wood chipper is used, a rule of thumb is that blades should be sharpened every 25 to 50 hours. However, it is best to consult the manufacturers' specifications.