This whole subject could be easily put to bed by calling your local
fuel polisher and asking the age of boats that need polishing.
I think you'll find all the 70's and 80's need cleaning and the 90's
will need cleaning in the next few years. Anything newer and there is no
problem. Meaning that if your system is clean, it's probably good for 20
years. At least, that's the way it is in the Puget Sound area. I suppose
warmer, more humid areas could be worse.
That said, I run dual Racors mainly because they were freebies and my
neighbor polished my fuel when I installed the Racors.

Gordon