If I read this correctly, it's your first full-time software job? Be careful about your assumptions. Just because your competitive new hire peers are hanging around until 9pm doesn't mean you have to. Every software company hires so many duds, if you come in and do your job well, and be willing to burn the midnight oil (not literally) for crunches, you will almost certainly not be fired. Focus on working effectively, signal that you're more efficient than your peers. Making it look like it takes 12 hours to get a day's work done does not reflect well on them.