[ZenGum]

TW, I think you need to read Big V's post again.

It may well be that spark plugs should never need replacing, that's the theory. Each car is it's own independent reality, and we've got to allow for the fact that quality control was pared back by MBA managers to save money, and that the car was built and serviced by humans. You know, those frail, irrational bags of mostly water?

It's like with the paperless office discussion. You're not allowing sufficiently for human fallibility.