I own a simulator that is an approved BATD by FAA. The approval is for 5 years (usual) and expires in 2021. I have had the device for years and it functions normally. The company that makes the simulator seems to be gone. I use the simulator to aid with instrument currency. Does the simulator become unusable for currency when the current FAA approval date comes or is that only for part 151 operations? It functions normally and has always. Is that approval date for the manufacturer or the user? I suppose this applies to many simulators out there. Does the manufacturer continue to have to exist and recertify for the older simulators to be used legally?