Honestly, for straight MD admissions, I would say that the most important thing is being able to talk intelligently and enthusiastically about your research. If you aren't enthusiastic and involved, it won't matter if you've been in the lab for a week or a decade...your interviewers won't be impressed by the experience. Likewise, a large number of weekly hours isn't enough by itself to make your research time impressive.
Work on talking about your research, and sounding happy about it. That's the most important thing you can do at this point.