There is no doubt that freshly sharpened blades lose their edge quickly. There is also no doubt that most people do a really poor job of how often they sharpen mower blades. Most of the blades that I sharpen for customers are beat to hell and back. Wouldn’t cut hot butter. Also, the longer you leave blades on and the more stuff they hit, the harder it is to remove them. The condition of some of these blades is pitiful actually. Ripping the grass and not cutting it, resulting in poor cut quality, longer mowing times, and unhealthy for the grass.After everyone has sharpened their blades to that nice razors edge at the angle of your choice mow for about 10 minutes and check the edge and see how sharp it is. Rotary mowers don't cut grass as much as rip it. Sharper is better but blades round over in a matter of minutes. Ever notice new blades aren't that sharp? No reason for them to be super sharp.