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My understanding is the fuel line in the tank is not directly on the bottom. So you're always "blending in" the last bit of previous gas (or water/ethanol) at the bottom of your tank at each fill up.
My sock sits at the bottom inside the tank sump. When I fuel up, it is usually with a full load of fuel since I am running on empty when I gas up. As such, if it suddenly runs bad, I know what it is. For some reason, you seem to be getting a bad load of gas more often than I have noticed in my cars. Even when I was driving 200 miles a day, the worst I have gotten is lower powered diesel. It doesn't run bad but the mpg goes down the toilet.
Another side story is I had an old beater that used to run bad every so often. Thought it was bad gas so put gas dry when it was running bad and it went away. One winter night after a long drive, I put gas dry in it and drove on. Floorboard was very warm Look underneath and the cat was glowing red. Every time I stopped and put the gas dry, it allowed the cat to cool down and start the cycle. Cut cat and life was good.
If you have a good gas cap that seals and the drain line is working in the filler cap compartment it seems pretty hard to get water in the tank. The only problems I have ever had was with very high octane racing fuels. They are very high in volatile aromatic hydrocarbons and when they evaporate away the fuel is useless. VP C16 and similar the worst at needing to be fresh but when they are they are magic if you have a need for them otherwise money flushed down the drain.