After 9 years of mowing rocks, boulders, bricks, cables, rope, empty paint tins, and various other hidden "gems" around our farm, I finally decided that there can't possibly be any more hidden surprises left by the previous farm owner, and I've changed the three abused and battered blades on my tractor mower. The old ones came off surprisingly easily once I'd put my Parkside 1/2" impact wrench on the bolts.
Apart from getting a better mulch when cutting, it'll actually save a little in tractor diesel because the mower won't get so bogged down.