I’ll also add my “leave it alone” if it works... mine failed shortly after having John Carrillo service it , no fault of his. The tank began leaking The cost , by a knowledgeable service guy near Palm Springs was $7500 to pull and rebuild mine with a new tank and copper tubing using my old burner ( he rebuilt it new bearings etc) , pumps etc
The recomended service is to replace the jet nozzle , check the spark gap ( tool is mounted on side of the burner) wire brush the soot off the interior burner tube and change the fuel filter. I was hands on involved in the rebuild and while I feel much more comfortable with it now, there are lots of things you can mess up.For example The burner hold down tabs can break off with too much torque or maybe “just because” they are weak ... the less times you disassemble the better IMO.
I bought and keep a service kit handy and will wait for it to need service, normally by starting to smoke. Like many things things that sit unused, the part time user may need more frequent care. We full time and the burner is on 24/7 . almost 1 1/2 years and still going strong and is smoke free still with no strong odor. I love hydronic boilers but hate the expensive repairs.