Install an output filter. They shut off if trying to process solids. Cheap bed insurance and have proven not troublesome in any way up here in eastern Canada. They are well designed.
Fifty to seventy five dollars for the part.

I think there is no specific cleanout recomendation. Depends on too many variables. But every five years for a start will give some indication of the need to do cycle. The septic guy that cleans your unit out may be the best source of information for your own individual cycle after he cleans it the first time.

Three years is now being recommended locally but on average may be too often. The regulation beds have become very expensive locally. You have to protect them. Any future bed problems and I will avoid the regulatory circus that now exists .

They have gone insane with their power. No common sense at all. Yet common sense when installing one was the most important qualification for all my life. Nobody with a brain wants one that represents a health hazard or does not work properly.