Is it an aerobic system that pumps the clear water out or just a regular tank? Ours is a grandfathered septic and we usually have to pump it ever 5-6 years. I made some improvements in the tank piping and expanded the field lines a few years ago so we may get 10 years out of it this time. Only time we ever have trouble otherwise is when the sister in law stays a few days. She thinks she needs two long hot showers ever day. (Insert rude comment here).
Big thing is to minimize paper and trash of course, and don't use those toilet bowl hanger cleaners, women like so well. Put some Rid-X in it once in awhile and flush spoiled milk down it to feed your bugs in the tank. You shouldn't have any trouble.
