I go to a 1.5 year Systems based preclinical w/ USMLE Step1 after Core rotations. Furthermore, we get an entire summer off between M1 and M2. I just finished my M1 year so i am ~2 weeks into summer right now.
I have close friends who have been doing Zanki since Day 1 and for these guys they will keep up with their reviews and perhaps even learn new cards over the summer. Personally, I haven't used Flashcards in Med school but I want to familiarize myself with it since our next 2 blocks are pure rote memorization. Just really not in love with the idea of doing flashcards. Plus I am really not convinced on the yield of Step studying now with the way our curriculum is set up since we will be on the wards before taking it.
Plan for summer so far has been doing research and going through clinical cases w/ podcasts such as CPS, Curbsiders, EMCrit, IBCC, and others. I find this style of learning for me works best. I also plan on reviewing my notes especially from beginning of Med school and developing schema for how to think about clinical cases for the systems we have completed. Might even make Anki cards for Anatomy, and Embryology.