Hi Straker! to answer your question regarding SGI Kits. The parts that need maintaining are the Filters which you have to change every 10,000km, Diaphragms inside the vaporizer (cleaning), O-rings due to wear and tear. For the ECU it should last you a long time. The only real concern is choosing the kit to be installed on your system. Each kit manufacturer has their own ECU's so calibrating can only be done by the installer because there is a software involved.
During most LPG failures the system will pick-up the fault and switch you automatically back to gasoline. This should always be the case in these kinds of situations. the change over switch for SGI kits can also be used for manual shifting back to gasoline.