On our 250 Bandits we roatate our knives every week or two.Depends on how dinged up thy are. Once a full roatation is over we send them out to be sharpend.
One of the specifications in the grinding is ( not to grind out all the dings epecially if some are deep.) More importantly, they grind the same amount off each set of knives so we're not tossing just one at a time and the knives are cutting the wood correctly. If I'm correct, I think the knife is done at 1/13/16 from center of hole.
Once there thrown out, new bolts and nuts are put back on with a fresh set and aval is reset. Although, anval should be reset after each sharpening.
So the the actual time ? Could be three or four months, could be a month . Depending on if the we're feeding alot of deadwood or feeding in gutter sweepings with rocks. Not suppose to , but the crew gets lazy sometimes.
Thanks
Greg