They have a useful but limited life. Just because they TURN, does not mean they are good. Bad bearings can turn easier than NEW bearings. As a matter of fact, most small to mid-range machinery manufacturers, usually supply as original equipment, inexpensive standard bearings in their machines. When replacing your bearings, ask your dealer to supply you with the next grade or two higher in bearing quality, it is worth it.
Bad bearings wobble.
That is the easiest way to explain it, they wobble from wear. They are ready to go. We do not make hook and skip tooth blades. The skip and hook designs that are used in carbon bands today, are 45 year old or older basic metal cutting designs. The fact that they cut wood is secondary.