I'll offer my 2 cents here. I was very involved in research all throughout college. About 15 hrs/week sophomore and junior year and about 20-25 hrs/week senior year. A typically pre-med's life in college is a mix of classes, volunteering, work, and ECs. Now try to throw research into that mix and it can drive you crazy. It's not that adding 10-15 hrs/week is devastating, but it will really throw off your schedule, and your samples don't care about your schedule.
See you might be busy 9a-11a volunteering, then have class 1:30p-5p, then have ECs 6p-8p. The next day might be totally different. Suddenly you're getting off volunteering and rushing to the lab to prepare an experiment to run while you're in class. Maybe it requires a small change every 2 hours. Now you're running to lab to collect a sample or change the temperature between classes. You'll probably try to finish up the experiment from 5-6, but don't be surprised if it takes longer than expected and makes you late. Now go to your ECs, head home, and finish your homework. Some days will be better than others, but this is about what you can expect.
Ideally you would spend 5 hours on research 2-3 times a week, but like I said before, your samples don't care about your schedule. Your cells need maintenance all the time, and your experiments will have varying time points. Sure, maybe you only have to do 15 minutes of work every hour for an experiment, but lugging between the lab and library/office every hour is going to lead to really unproductive studying. Even beyond lab time there will be a constant need to read relevant papers. Probably at least 1 paper per week, which will take 2-3 hours. Then there will be the million experiments you should be doing but don't have time to do. Essentially it comes down to this: you just won't have the schedule space during undergrad to do research the right way. If you care about your work, this will bother you. Personally, I found that adding research basically took any free time and tore it to shreds. Then again, I was "lucky" enough to always have been put on my own project, which I think is unreasonable in undergrad unless your only other distraction is classwork and minimal ECs (the case for most pre-PhDs) or your project is particularly schedule friendly. It's possible to do this with your other activities. I did it, managed a few posters, abstracts, and awards, and still managed a good GPA and solid ECs, but I still never published a paper, and I felt scatterbrained, rushed, and behind almost all the time.
Find a lab where you will start working solidly under a graduate student or post-doc doing actual research. Being a petri dish cleaner is a waste of your time, and working on your own project is the blackhole time-sink I described above, and you could still end up going 3 years without any deliverables. Have a schedule in place where you work specific hours in the week but are still involved enough to get on a manuscript. Try to stay involved in the same lab for at least two years. My biggest mistake was switching around too much. I wouldn't have regretted this if I had ultimately decided on research, but if you don't want this for a career then the only thing you care about are deliverables (papers, posters, awards, etc...), which you get only with sustained involvement or luck. The best research experiences I had were over the summer. During the semester there are too many distractions to do high-quality research, but if you can make it like any other activity (i.e. 3-5 M-F) it will be far more tolerable and you can put in enough time for a co-authorship, just hope your grad student/post-doc is smart enough to put together good experiments.
