If you'd really like to know...
My undergrad years went kinda like this:
Monday-Friday: classes scattered throughout the day between 8am to 7pm, 18 credit hours per semester. Day was filled working on wet lab research, computational stuff, clinical research, etc. About an hour or two of downtime each day was spent reviewing class notes. I'd come home at night and review for another hour or two depending on the workload.
I'd volunteer one of those evenings for several hours. On another morning in the week I'd be doing clinical research at a local hospital. On weekends, I worked open to close (approx 24 hours). Some weeks, I'd work a shift or two during the weekdays (40ish hours total).
I took a few classes over the summer too, while doing research fellowships and studying for the MCAT. Any free time I had was spent doing hobbies with my close friends.
The freshman year transition was hard, but I managed a 4.0 the other three years. After a while, the classes were getting very difficult, but managing the workload became progressively easier. I kinda just felt "numb" to it and wasn't really that stressed during my junior/senior years, even though there was always a ton going on and I never had days off.
Overall, I don't regret anything. I'm sure I could have eased down on the workload, but it has been taken very well by the schools I've interviewed and been accepted at. It has always been a topic of discussion, and I think some of my letter writers talked about it from the way my interviews seemed to go so far. I'm now enjoying my gap year, catching up on some things I didn't get to do (traveling!!!!!! Oh and tons of metal concerts).
I definitely feel very confident to handle whatever crazy schedule med school throws at me. I'm sure it will be tough and I will struggle, but having a proven track record of bouncing back with many responsibilities makes me feel more than ready to kick butt.