My '98 Duratec started misfiring at 35,000 miles and the dealer said I needed plugs and wires (which were installed and the car ran fine.)
My '97 Zetec has 68,000 miles and is running fine with the original plugs and wires.
When I pointed out this discrepancy to the dealer he said it's perfectly normal to have to replace plugs/wires at 35,000 and it's also perfectly normal to have the original plugs and wires last 100,000 miles.
Oh. Now I understand.
