[neallewis]

Any of the yokomo idlers can fail, but this is reduced to never if the top shaft bearings are inspected and kept in good condition, and the gearbox is kept clean and lubed with a touch of lithium or other anti-wear grease.

I've seen topshaft and idlers totally destroyed, in cars that have had no maintenance, but the kit parts are absolutely fine if maintained, as with any other parts on any car.