Good point. In any case, it comes down to good maintenance. Cedar Point and the other seasonal Cedar Fair parks do a complete tear down of their coaster trains and other ride vehicles every winter.
As if anyone had a hard time figuring out, I hold Cedar Point to a very high bar for safety and operations. They can run a park, be extremely safe, have VERY high throughput (Gate Keeper, Valravn, Millennium Force, and Maverick crews are the stand outs this year for me), and have very little down time (20 minutes max for most issues. They replaced Dragsters cable in record time a few years ago and replaced part of the launch system and roll-back brakes in record time this season!). When I see poor operations, I think how CF would be doing it.
I do wonder how often, if at all, Disney does tear downs on their coaster trains. Space Mountain has several trains so I'm sure they could do it easily. RnRC on the other hand, I'm not sure if that is ever stripped down with the exception of refurbs (IF it happens then). Regardless, new trains for RnRC would be great.