Going on fourth winter, with oil fired ek 1........nice unit very fast quiet and efficient////////had problems with lighning strikes on hilltop house.....blew out computer on furnace,3x. AS for longevity who knows? energy kinetics has good tech help and decent proration on pressure vessel..........alot of guys don't like them because they are non traditional and have not learned how they function. I burn 750 gallons in 2800 square foot house ,mega foam insulation, with radiant heat , we keep thermostats at 65 degrees and we live in nh pretty good!.....by the way the digital energy managers that popped were under five year warranty.......I like mine.