www.christianrepair.com from Tilton are totally super-duper, click on SERVICES, and work on propane and natural gas (Laconia) and apparently have stopped working with heating oil and kerosene.
For forever reliability, the Rinnai direct vent, hot air space heaters seem to just go for years and years without needing any service and create very comfy warm breathable hot air.
If you have a hot water, oil fuel central heat system with radiators or baseboards in a big house, installing a Rinnai propane direct vent on the first floor in an open space like a living room, den, kitchen or dining room works good to compliment the central main system since it heats up fast and really feels good. Will soon become the most popular winter spot in the house.