One answer to one of the unknown questions:
laboratory testing is required when Jet A-1 has been stored and not added to for a period of six months or when aviation gasoline AVGAS has been stored and not added to for a period of three months
So basically, you need a fuel delivery every 3 months. Now here is the mad thing, I asked how much needs to be delivered and the answer was “some” - ie. you could take a 20L delivery and that would refresh the 3 month requirement!!