Don't run the fuel tank dry and wait till the car stops. All that does is cause it to run lean at the end and lean means wear. You shouldn't really leave any fuel sitting in the tank either because that will attract water into it and you don't really want water running through the engine either.
I see it mentioned that an engine is started in the same state as if it were run out of fuel. This is why an ARO should be used because it leaves a nice oil coating on all the moving friction causing parts. Most fuels these days are formulated to leave a lubricating film behind to help protect the engine, but in my opinion an ARO should be used. ARO also helps to keep any moisture making contact with the engine parts and cuts down on corrosion.
If you've got a DX3s then it has a timer function. So fill your tank, start your engine and start the timer. Monitor how long it is till the tank is very nearly empty and then you can set the timer to give you an alarm when you need to fill up or stop the engine.
It's a simple matter of look after the engine properly and it will give you very many hours of enjoyment, and at the end of the day, that's what this hobby is about.