For touch ups I use this little carbide knife sharpener. It has two carbide inserts, handle, and cuts on the pull stroke. It works. Machine shop for sharpening.
I touched up my blades, yesterday. 5 minutes of work. Great results.
I don't recall how long it's been since changing blades.
I am very diligent about only chipping clean material, hauling off dirty rakings that have gravel.
I don't chip like many people, here, do. Limbs are commonly under 6" in diameter and relatively soft. Almost no dense hardwoods.
My ignition coil died two weeks ago. I grabbed a rental bc700 for a couple hours for a storm cleanup of geary oak and madrona, very hard and dense woods, locally.
What a slow, Pain in the neck.
We were both happy to have my usual chipper back.
I needed to sharpen up when brushy elm clogged my discharge chute.
My anvil gap is probably not optimal.
Brushy birch, not run through at a fast enough rpm is a clogger.
Better cutting seemed to greatly increase my discharge... not apples to oranges, as my throttle control is not marked for the range in which it can operate. Seemed to corollate, though.