I called my dealer to arrange a service for my 91 Accord, which just
turned 100,000. The service person says that they don't have any
records for the car and explained that the system wipes records for
any car that hasn't be serviced in six months.

I'm a computer programmer and nothing is cheaper than disk space these
days, and I could likely fit all of the maintenance records of all the
Accords in the US on one of my PCs. It just doesn't make any sense
that they would wipe out stuff.

I don't do much maintenance of the car at the dealer, but the car was
originally bought there by the previous owner and I have had it there
several times. The original owner had all of the maintenance done
there.