Ive seen time and heat cycles are more of a killer in the plastic gear them actual miles.

You might as well be concerned with the water pump and as well the alternator.

About a year ago I went and got a truck with 100k miles on it and had to replace both on the drive home, next time I will replace prior to the trip or pack a spare.

When I did tear it down, concerning the chain and plastic sprocket it was one of those "how did it make it" moments as it was worn, chipped and the chain hanging lower the a 100 year old mans nuts.

So even if possible spending a day to swap out some parts might be a thought, beats a auto zone parking lot like I had to do.