A lot of it just depends on how efficient you are.
Typically, I'd say I bill between 7 to 8 hours in a 10 hour day. If I want to take a vacation, I have to bank some hours by working later nights, or taking work with me. One trick I found, is to get on a team that is going to trial. During the trial prep period, you are working incredibly long hours. There have been times I slept in the office. The upside to this is, you can bill 16 hours in a day. The trial can go on for a long time, and you will have the billable hours of a superstar. Last trial, I was able to average about 12.5 hours a day for about 6 weeks. A few weeks, came out with over 90 billable hours. In a matter of 6 weeks, I had about 525 billable hours under my belt. This allowed me to take a few vacations and still be on pace to hit my quota. There are periods where you are grinding it out, and you will have awesome time/service reports. During the slower weeks, you have to make sure you are having projects fed to you so you don't fall behind. Last year, I billed about 1800 hours, and managed to take two vacations of 9 days each. Went home at 5:30 plenty of days, didn't go home at all on others...