I have found that the blades on flip over saws last incredibly well but inevitably there will come a day when you need to resharpen or better still buy a second blade, if only to save your poor struggling motor!
Buying a second blade enables you to have your original blade sharpened at your local tool shop/merchant. This can take up to a week for most places, hence the need to wait for that second blade unless you can manage without your saw for a week (no way!)
Having a sharp back up blade in stock means that you need never struggle with a blunt/dangerous blade ever again.
I find that having a blade re-sharpened costs less than a quarter of a new cheapish blade, making it economically viable to sharpen a few times as well as being kinder to the environment!