Don't overlook "spare parts" as an 'unnecessary frill'. A spare timer motor is very short money, and a blower/gearbox drive motor is a nice spare.
I know for the most part things can get there overnight, but why tax you brain or worry? The couple hundred you invest will pay back in spades down the road.......on a cold snowy, icy day.
Do as you wish, but I keep antifreeze in my trucks, a spare belt or belts, bulbs, etc........and tools also. A couple LED flashlights.......why not? I can also mention that Keystoker is excellent to deal with, however so are Axeman Anderson, AHS, Alaska, Leisure Line, and most of the others. I did not mention Harman, however I have two dealers in NH that are excellent. Generally as an Industry, the Coal Folks are excellent at all levels. Even the retired 'Old Timers' are pretty darn good about sharing info.
My vote says: Order spares, test them when they arrive, store them appropriately, and sleep well because of it.