The generator should as long as it has adequate cooling only ever need new bearings. The model two stroke can be surprisingly reliable if treated right. It will not be screaming its head off but at a fairly constant speed. No prop loads helps. The big flat four has a much nicer balance than singles or twins and only runs 7.5 cr, it has a lowish mean piston speed and will not be run constantly at max output. This all helps for reliability. In actual use it would spend only a tiny %of time anywhere near max power and mostly be running at approx 50%. If it is cooled well, fueled well and given quality oil, it should be good for 25 hour inspections and the rings at 50-100 hrs. That is real conservative. It will not be subject to the loads and g forces of a full aerobatic regime model aircraft. In operation it should be able to do 200hrs if done right. For most of us that is a lot of flying. Super long life is not the point, it is cheap and experimental. Easily fixed and part of a backup charging system. The fundamentals of the design are no different to a small rotax or any number of other small two strokes. Sure a GX Honda can be reliable but the power and weight do not suit a hybrid application. The extra weight is a lot of spare fuel and or battery capacity to overcome power loss in flight. That extra mass of kg is a lot of battery to get you safely down if the hybrid dies mid flight. Running a GX is only really viable as a standalone gas engine with prop attached.