While I agree with this post generally, bear in mind that there are MANY 45-55 hour per week jobs and careers out there, which offer a significant amount of free time. There are also jobs out there where you have weekends off and no "homework". Some of these are professions. Medicine and law are usually not these. There are many happy people who don't go into medicine or law. Folks on SDN sometimes get too bogged down in the major professions and don't check out that there are other career paths out there as well. You have to decide what things are important to you, and if major blocks of free time in the near future is of major importance, then maybe premed isn't the right path.
In med school you will be doing some amount of studying every day, and will lose countless weekends to the library. Third year, you will start to have late night or overnight rotations. Residency you will be working 80 hours weeks (limited to that by law, but will be expected to read up on things on your own in your "spare time" on top of that).
The people who are really into medicine love it -- thrive on it. The folks who are into lots of free time, or those who didn't have a clear sense of what they were getting into, or those who are trying to "serve their sentence" in hopes of cashing in in a lucrative sub-specialty down the road in the distant future tend to be miserable. Know thyself.