How many times can you sharpen most chainsaw blades before you have to throw them away?

It is according to what you are cutting and how much you file the blades. would guess between 20 to 40 times. Some of the electric files are good if you are not accustomed to filing blades but you need to know how to use manual file as you may be in woods etc. Normally it is quicker to just file the blade rather than replacing while in field. How quick you dull the blade is also what you are cutting and how good a job you did on filing.