I have mine at 16/8 and it seems to work fine. I am a firm believer in giving them some rest. There are some new auto strains out there that do fine with 12/12. DNA has come up with a 60 day Lemon Auto that needs no special light or cylce. 12/12 is just fine but they claim that it will do good just sitting on your window.
My decision to keep mine at 16/8 has to do with operational costs more than anything. I was an 18/6 guy but for the strain I have been growing (NYCD) the 2 extra hours of darkness doesn't seem to hurt. Had similar dry weight after each cycle. That's an extra 14 hours a week that my lights are off. Saves my electric bill and my lights last a bit longer.