You will find advice all over the place.
My practice is to not put large amounts of grease down the drain, I'll pour into the woods.
Those who (supposedly) are in the know say to not use commercial tank cleaners as those just allow the solids to re-solidify in the leach field, not good.
We put yeast down the system a few times a year when we will be away for a several days. This allows the bacteria to regenerate naturally and do the work they do so well when not killed with chemicals.
I have had advice to have the tank pumped that ranges from yearly to every ten years. The tank cleaning service said every seven years. I am scheduling for every five years.
Factors dictating frequency of cleaning are size of tank and size of family. e.g. a family of eight using a 500 gal. tank needs it more often than a retired family of two with a 1000 gal. tank.
"Folks is funny critters."
Think for yourselves and let others enjoy the privilege to do so, too. ~Voltaire