I wouldn't literally use it the first day of class and/or use it every day as a M1 that's not efficient. I would buy First aid whatever the new edition is (first aid is honestly dirt cheap anyone and their momma could buy it). I would learn the class material during the weekday very well and then set aside a couple hours during the weekend or every other weekend grab First aid to go over the material covered in class but more importantly to help you focus your studies. You really won't have to reannotate that stuff into another copy of first aid the next year, you will honestly know it so well that just by looking at it everything will kind of click. Plus the point of using First aid over the weekend during M1 is not to memorize this all the way till step 1 date but exactly what Bucket said in the last post, it's so you can narrow down to what's the most high yield information. Especially during M1 you're going to get taught a lot of junk that's not important and it's essential to go through the rubbish and pick out the high yield.
For example there's 11-12 glycogen storage diseases during my Biochemistry class the PhD professor taught us 8 of them but first aid only has the main 4 glycogen storage diseases. So instead of using my brain power to engrain 8 storage diseases why not focus A LOT on the first 4 glycogen storage diseases which are the most clinically important and most important for USMLE Step 1 and spend a less time on the extra junk. Hell I would really try to understand conceptually the first 4, learn them well and kind of cram the last 4 just for the sake of the class and still be efficient.
I honestly believe using First Aid during M1 year maybe (once every other weekend) and using First aid every weekend during M2 year even if it's 1 hour can really focus you on the high yield information and make your life much easier when actual board prep comes at the end of M2 year. If you used first aid the first 2 years and got a couple passes before board prep man you'll be breezing through first aid.
While going over Biochemistry in First aid I realized that I recalled a bunch of junk that's not even important but couldn't remember the important stuff and I was thinking to myself if only I had used first aid during M1 year and just been more focused I wouldn't be in this crappy situation.
There's a lot of stuff they taught us in Physiology, Immunology (2 relatively important topics) that's not in first aid and is not important so M1 really is ehhh such a boring, crappy year lol
Right now I have tons of exams, I have to study for boards and the whole relearning the important stuff from M1 has become a huge annoyance.