you can actually over a period of time take too much off one side and cause the blade to be out of balance there fore causing problems on the motor.
I usually sharpen a blade with a hand file and know that I am not taking off too much. After 5 or so sharpenings, get a new blade.
You know mulchers are great but many do not realize that when mowing and your not taking too much off, the blade really does not have to mulch. It does mulch when removing more than the normal 1/3 of the grass that you should only achieve to remove, then the grass goes into shock for a while.