Tony, that philosophy is a good one. Many years ago one of the car magazines had an article about keeping a vehicle for a long time, and the key for them was preemptive removal of parts.

The idea was if statistically an alternator was going to go 90K miles (they had all sorts of numbers), then changing it out for $100 at 80K miles only lost 9% of it's life (value $9), but kept you from ever being stranded which could set you back far more. And you as the owner chose the time and place for the maintenance--exactly what you are doing.

DAN