I don't have many stoker customers anymore, but the burner plates were #1 as far as failure. I used to attribute that to lack of clean-out lever use by the homeowner. Feed tubes, worms and tube couplings were big also.
I have never replaced any parts in the actual stoker drive area.Just burner motor/fan/coupling, and worm components.
The furnace will see alot more wear as sitting all summer is a killer. The boiler stays better if run for domestic all year.
Since the re-introduction of the furnace, I'd like to remind any furnace owners that it is imperitive that the unit gets serviced imediately after shut down in the spring.When we get done with the cleaning, we spray down the furnace interior with wd-40 and leave both doors open.