I have a BC1000XL I bought used with about 1800 hours. When I first bought it the knives seemed relatively sharp. They don't seem to have gotten any duller and I have put about 75 hours on it. The manual says if the knives warp under a straightedge to change them before using the machine again. They also say to change them if the holes where the knife bolts go in have any cracks around them. Neither of those things are a problem. The manual says to change them every 10 hours, but it can be much more or less depending on usage. The belt is tension ed just as it should be. I have never put anything in the machine bigger than 10 inches in diameter, and most of the stuff I do put in is smaller than 6. I use the machine part time and mostly baby it. The only metal thing that I'm aware has ever been put in the machine is a very small "non climbing" carabiner that got sucked in with some brush. Other than that one knife seems to be in good shape and the other has 3 indentations about 1/16" deep and 1/4" wide. (I guess from a rock or piece of steel?) The Smartfeed almost never gets used. I had a Vermeer mechanic tell me one time if the knife edge feels like it has been rolled over than the knives need replaced, but they don't feel rolled over. The other side of the knives is razor sharp. I have the right torque wrench but don't have a breaker bar big enough to get the bolts out. If they need replaced, I don't have any problem doing it myself and I have a manual and am willing to learn the process to do it. I am just looking for the best indicator of them needing replaced or flipped. I also know not to reuse the bolts anymore than once. Any advice about the knives on a BC1000XL is appreciated. Thanks