In over 50 years of owning boats and I have never cleaned a gas tank. Unless you know you have a problem I wouldn't worry about it.
You can take a look at your used fuel filters, even dissect them, and see if they are picking up a lot of contamination. If they look decent I wouldn't worry about it.
I do put some dry gas in during the spring in case winter condensation has caused water droplets to invade the gas tank.
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