That's a fair point Hadrian. I can't remember the last time I changed a spark plug. Modern ones go on for years. I haven't checked the B Max service schedule but I don't even think they got changed in the 1, 2 or 3 year main dealer services. Back in the 70s and 80s we would change them at every yearly service and annoyingly, sometimes a new set of Champions or NGKs would come with one duff one. in those days they were quite cheap so and it was considered a false economy to skimp. Previously on 2 stroke engines, I seemed to be forever replacing spark plugs.
Not only that, but I used to take them out from time to time to check the colour of them with the old carburettor engines just to make sure that the mixture was right.
B Max Titanium X 1.0 125 bhp in Magnetic with built in SatNav and rear sensors.