To add to the chorus, I have a PhD in a biomed science. I finished in 5.5 years, and that was approximately 40-50 hours of lab time per week (including some very early mornings, evenings, and weekends) plus another 10-20 hours of study, data analysis, and writing at home. My advisor and I had a long-standing Friday night ritual wherein I booked time on popular equipment from 6-8 PM, collected my data from experiments that I'd spent all week setting up (using models that I'd spent a couple of years developing), went home, ate dinner, did the preliminary data analysis, uploaded that to the server, and then went back and forth via email with the advisor as he picked apart the data from his home (depending on the results and his mood, this could go until midnight). I loved what I did and have absolutely no regrets, but it was very hard work, a true labor of love.
There's no coasting through a PhD. A decent dissertation committee will not allow that. However, if you are willing to work hard and truly love the subject, I certainly won't discourage you. I'm still amazed that I got to spend 5.5 years getting paid to do work that I loved AND came out with a doctorate. If you simply like the idea of making $25K per year to work in a lab, I'd recommend applying for research assistant positions. I did that for 5 years before going back to school, and I enjoyed it immensely.