Nah, they don't care. Most people only shadow during stuff like winter break (if they're lucky to find a doctor still opening up their clinic). Only thing that matters for other experience is:
-Depth of experience over breadth.
Staying at one hospital, even if on and off during breaks/semesters/ for as long as possible > jumping every 2 months to a new hospital to fill up lines on your application and say you volunteered all across the land. I know people who did the latter and it looks trashy, lame, uncommitted, and pretty much is the equivalent of being a premed slut
-Hours.
I view shadowing in my opinion, as a separate category than "clinical experience" (I usually reserve that word for like stuff you do). But nevertheless, shadowing is VERY important, and pseudo-mandatory. For shadowing, I think like 30-50 hours is sufficient so you know what you're getting yourself into (they ask about that). It's also kinda interesting and motivating. For "clinical experience" (where you get to do stuff, like volunteering, being in a clinic) I have my own very unofficial heuristic. I call it the triple digit rule. 100 hours+, and you should be good. Don't jam 100 hours in like a summer and then go cold turkey until you apply, either. See depth above.
