Originally Posted by datlas

I was speaking with a clubmate today on today's ride. She had been having all types of "problems" with her drivetrain, not shifting right, skipping etc.
She took it to the LBS. Turns out she had not changed her chain in over 3.5 years!! And this person rides about 5K miles/year. She was complaining that they had to not only change the chain but the cassette and chainrings and RD pulleys. I told her chains are cheap, and to use a ruler to measure and change them when they get beyond say 0.75% and/or at LEAST yearly.

She said only "a few" of her cogs/chainring teeth were really shark-finned. I advised that any is too many. I hope she gets it now.