I have planed about 700-800 bf of lumber using my Dewalt 13 inch planer using the current blades. During my last time using the planer, the reset switch clicked out three different times. I was using cherry which is soft and only removing 1/64 (1/8 turn) at a time so i do not think it was taking off too much material. The surface still looks good on lumber so I am not sure if the blades are getting too dull or not. How do I know when it is time?