There are products you can use that break down the sludge in septic tanks so that you don't have to get them pumped. Its base is bacteria, which breaks down the sludge, and keeps the tank and septic lines moving. So I am told...I'm going on 5 years using this stuff and no problems with the septic tank...
4 years ago when I had it pumped...turned out the guy doing the pumping was a good friend from yesteryear, he said "dude, why are you paying my company $250 to pump your septic? Just go to Home Depot and use the bacterial stuff, you won't need it pumped again"
Hoping someone with more knowledge than I can confirm this.