Yep, adding extra to your leech field if possible is always a good idea.
Pumping your tanks out is totally dependent on how many people use the system and how good / bad their habits are. If you are putting stuff down the drain that you shouldn't be, then your sludge will build up much faster than if you paid attention to what you were flushing.
Sticking your tanks is the best way, that way you know exactly how much sludge has accumulated in the bottom of the tank(s)...
But a general rule of thumb, I would do it *at least* every 3-5 years as a bare minimum. It doesn't cost *that* much and it's important to inspect the tanks too for damage and making sure your pipes are okay. Usually once you realize you have a problem, the cost has already skyrocketed when a little preventative maintenance would have only been a fraction of that.
Anaerobic system (i.e. traditional gravity systems) the bacteria digests things very very slowly because there is no oxygen. The liquid going out to the leech field is still being processed and still smells pretty bad.
Aerobic plants have bubblers to add oxygen into the water and thus allow aerobic bacteria to grow. They digest the waste much faster and are much more efficient at their job. The water coming out of those usually just has a little musty smell but is much more clear and safer for the environment. Often the water is used to irrigate flower beds, or it can be pumped into a leech field, or some places even allow discharge directly into ditches / creeks...
Our commercial property we have both systems. One of our gravity systems the leech field was failing and during the winter the system would back up because the field would just get saturated. One nice thing about the aerobic system with the holding tank & pump, if a toilet gets stuck open or someone leaves a faucet running, instead of saturating the field and causing problems like in a gravity system, it will just trigger the pump to come on and the sprinklers pop up and water the field. When that happens in the middle of the day then you know something is wrong and investigate.
