I've been working out of town for a couple weeks and just saw this post. 100% since October 19th, 1972.
The FIRST Arab Oil Embargo finished it for me. Yes I have oil boilers as a backup in each location, however they are not turned on, and are tested once a month.
Like Federal Express....when it absolutely, positively has to work every night, I do have a back-up. 4500 sq ft at home, other locations, more sq footage, bigger boilers.
Has one of my Coal Boilers ever failed? Not yet! I do keep belts, blowers, motors, gear boxes, chains and whatever I need on the shelf, because unlike today's "Just Right Timing", I believe in Murphy's Law and that does not work for me.