They are finicky creatures. If you are not going to keep running the 2AM clean out then put a tight cap over the outlet/inlet. I don't know what summer critters you have there but here it's yellow jackets. Of course, when you switch it on the usual groans of metal expansion are usual. However, if dirt gets into those little flame holes then the whole thing has to come apart and you will need to be sober for that rebuild. I know of one guy who runs heating oil and puts an extra tab heater on the inlet, in fact he swears that he can run veggie oil. That how Toyo changed the claim on the OM222 that they run on #2 just a bigger heater. Don't believe it, you will just make our local dealer rich. However, for fast local heat they are great but you need to supply TLC to live with them. Also you gotta get a good inlet filter such as a golden rod 5 micron add the filter replacement option with the water capture and that is even better.
Our local dealer became a personal friend but got out of the business. He complained that after people bought the units they would run it on any old #2 heating oil crap even though he told them only use kerosene from one local supplier and he got killed by service calls under warranty. Local bandits are diluting the kero with #2 to make extra cash and national standards don't catch that one - specs are very wide. Now we have no local dealers and repair guys charge a fortune to cover that one and I have to mail it to them. It's like Obama, hope for change seemed like a good idea at the time.