I just put in my 2 weeks at my firm last Tuesday and it's easily been the best week I've had in the last year. I haven't though about my hours once.
The only thing that you will be able to think about is work. Either you're working, or you feel guilty because you aren't working. Even when you sleep, you can't get away from it. I've had a lot of dreams about billable hours, partners rejecting my work product, getting fired, forgetting a deadline, etc.
We had monthly associate meetings where a different partner would come in each month and tell us we need to bill more. That was the topic of at least 75% of the meetings I've been to over the last 3 years.
Of course, the pressure to bill means that you won't be home until 9:00 or later every night. I get home, eat dinner with my wife, watch like an hour of TV, and then go to bed. That is your life. Weekends are largely consumed by working, so you can't go anywhere over the weekend. You may have several hours of time to yourself over the weekend, but you'll be so tired (and drunk from drowning your shitty life in alcohol) that you won't actually do anything other than lay around.
Beyond the hours and stress that comes from billing, the work environment sucks. You go to a partner for help and they are absolutely fucking useless. "This should be easy! it should take 15 minutes." Ok, well the 3 hours I've spent and gotten nowhere tends to refute that. No direction, no help, just glance and it and send you on your way. But they are happy to bitch if you don't do it exactly how they want. And by the way, they want it in a way that is directly opposed to other partners. You just said "teach" in your response because another partner always does? No, that is bad and you should feel bad. Don't you know anything about patent law? Haven't you read that random district court decision that came out in 2002 saying that "teach" has a certain meaning? And just what the hell did you spend 5 hours on this for anyway? Certainly not looking up the proper terminology! That partner that has been doing this since 1975 can crank out a response in 1.5 hours, why can't you? Oh, you're spending hours googling "how to be a patent attorney"? That's nice, but please get your efficiency up by the end of March because you're wasting too much time googling how to do your job. Got to get that 90%+ efficiency rating!