Tip from Susan:

After having to spend $100 on a new timer for a 4 year old dishwasher, I was told by the repairman that you should never turn the knob on your dishwasher when the door is shut. That sends electricity through the timer each time you turn the knob, and wears it out. So set it to whatever your setting is by turning the knob, and THEN shut and lock the door. Timer will last twice as long. Simple but I would never have known that.