Engine seals cannot be assured for such extended times, and are critical on a 912 .The Rotax parts are too expensive. On common aero engines wear rates are higher at higher hours often making the eventual overhaul more expensive. High hours engines are more sludgey making them more likely to fail on longer trips.. Higher hours engines have always been more failure prone. When a motor is removed and overhauled it still produces close to the rated power. It HAS to be able to do that . Aero engines operate at about 75% power most of the time and need full power to get into the air every time. No escaping that.. Military rated engines have much lower TBO's than the same engines used commercially. How the engine is operated has a big effect on it's life and reliability. Engines used only occasionally become pretty suspect . Stored engines should be inhibited and never just run now and again. Unless thoroughly warmed up (Usually about 45 mins air time) the motor will get excessive moisture in the oil. NEVER ever just run it briefly and leave it for weeks. The worst thing you can do. Nev