Something else to consider, riding style. A lot of people are mashers, they keep their bike in a higher gear which makes them pedal harder but slower. The problem with that is if the person pedaling is overweight, they put a LOT of torque on the wheels. My son killed more than 2 rear wheels with his mashing style of pedaling. He would be in the smallest cog in the rear and the middle on the front and start off from a dead stop going up a hill at his 300 pounds. That is going to put tremendous twisting torque on the rear wheel.
What I taught my son was to downshift the rear derailleur all the way while coming to a stop. He finally listened and even said how he found it much easier to ride now that he downshifts.
Just something to keep in mind.