LOLIt really is a self sustainable topic though if you think about it and one I am sure everyone interested in prepping/survival in place has thought about long and hard.
Well, septic tanks are a pain in the derriere. First, you have to hit it right when you are building the house. Then, everything has to work just so. The results if it doesn't are both disgusting and costly. Septic tank systems are one of those things where there are wildly different opinions on just about every aspect of the question. You can't trust what the commercial product makers say because they are just pimping their products. The best way to get a handle on it is a discussion like the one at your place. Even if there are different opinions, you can pick the one that makes the most sense to you.
We do have one. We haven't had any problems so far, thankfully, but we are due to have it pumped. It's been 7 1/2 years.
I've never had mine pumped, and haven't had any problems. But I lavished great care upon it, and for the last few years my wife and I have been the only ones here, so we aren't putting much pressure on it.