i dont think thats too bad, that stupid little fan motor sounds expensive but really to have on hand most of the parts that will fail for under 300 bucks i think your ahead. i plan on doing the same thing with my ka-6. i dont know of anything else that could really go wrong due to natural failure. i think i had a small hiccup with my aquastat, i think i priced that out at around 125? timer switch? maybe after 10+ yrs, i was hoping more guys would chime in and point out some other common failures.