I'm used to plastic gears lasting decades, but they are not like hardened steel, things can happen. Even steel can develop cracks years later, from something going wrong in the production. Since they talk so much of crumbling gears due to age, bad storage, climate, etc., I lean towards a new replacement. I know of someone who replaced the cam turning gear, and the rest of the machine were fine for years and years after, you can always experiment.