This mower was a High Weed Mower, but even if it were a brush cutter or standard lawn mower rental, blade performance is still important. It cuts a lot of very tall and overgrown grass each time it's used. They are an amazing work horse.
I sent it to our mechanic for blade sharpening. With some difficulty, our mechanic was able to unscrew the bolt holding on the blade. He then held the blade edges against a bench grinder and ground the blade down to perfect sharpness. Then he hung the blade on a nail that was sticking out of a vise. When the blade did not stay level and instead turned down to one side, he determined that it was out of balance and he ground/sharpened the blade some more on the opposite side.
That trick balanced the blade and helped prevent the the mower from shaking while in use. He did a bit of other regular maintenance then release the mower for rent. It may seem trivial, but a sharp blade can make a whole world of difference when mowing.