Well, quite often you'll be given keys to the building and the labs that you need to use so you can work all night if you need to, you just have to sign in. That's what they did for me on my degree project. It really depends on what you're doing though. Treat it like a full time job. If you have something to do, spend as much time as you need (Eevn if it does mean working til 10PM) if you've got nothing to do, hang around and look like you're doing something