Since I prefer a sewer, I am unsure as to proper septic maintenance - but isn't every 5 years rather infrequent?
And $500 every 5 years for upkeep doesn't seem $$$ to me.

I believe the tap fee for a single family residence in Walton County is about $5k.
Septic tank systems can last for decades, but it all depends on installation, upkeep, and environment.
Tallahassee is currently putting in sewage, at a very high cost, to the Killearn Lakes area. It was required due to the high red and pipe clay content in the area. The developer chose not to install sewer and things were fine for the first few years. However, as the area was completed and vacant lots gave way to new houses the ground was over saturated and couldn't handle the amount of waste being put through the ground. It resulted in backups and outright failures.
The majority of septic tanks are installed correctly and with very little maintenance (you flush an enzyme down the toilet every 6 months to a year) and will only require maintenance when compounds that are not digestible become to concentrated. Fats, soaps, and some "fibers" are the most common culprits. Once those become too concentrated the tank must be drained via a large pumping truck. If this is not done the compounds can backup into the drain field and clog it. This prevents water from everyday use and rain to become trapped in the tank until it overflows. Anybody who's ever been through this knows it's not fun. If you saw what happened last week in front of the Whitney Bank in Seagrove that's akin to what happens when a septic tank fails, after every rain fall.
One of the issues with this law is the lack of knowledge the average person has regarding their septic system. Potential an unscrupulous contractor could inform you every 5 years that the entire system needs pumping or even replacing.