I heard that plastic gas tanks deteriorate and clog carbs.
I can only speak from my own experience of having plastic tanks on many motorcycles and outboards for over 40 years. the only fuel related problems I have had were related to forgetting to drain the carb for long periods of time.
There are probably many different types of plastic tanks so it may be a possibility? If they deteriorate you could probably see the debris in the tank or they may start to leak?, which would be very bad, especially with a permanently mounted tank.