Replacing your lawn mower blade every year or two is essential to keeping your grass looking sharp. Keeping your lawn mower blade sharp is important. Prepping your lawn mower blade, either sharpening it or swapping in a new one, should be a part of your spring lawn season prep. If you aren’t sharpening your lawn mower blade, it’s a good idea to change it every season. Selecting Your BladesBefore you go out and buy a replacement lawn mower blade, make sure you know what you’re looking for.