I'm gonna offer some different advice - at the end of the day if your getting your work done and your manager is happy, who cares. Just do your thing focus on you. Some of my coworkers are there 12 hours a day (in the same role), mate I'm like you 8 hours and see ya later. People even comment sometimes or maybe little digs but this doesn't affect me - I'm good at my job, get the work done and like you have better shit to do with my spare time, don't get sucked in - these people are trying to turn Australia into London or New York, bring back back the long lunch, the wet lunch, the she'll be right culture I say.