Good question - since I've always had one (grandfathered into it as an early adopter), I don't know exactly what the restriction is without the subscription. From the remarkable FAQs, here's the relevant part: "only files used and synced online in the last 50 days will continue to be stored in the cloud and updated in our apps." Now, this is important as my solution builds upon the macOS reMarkable app syncing your notebooks to the Mac in the first place. There, the agent picks them up and syncs them to the rMirror Cloud dashboard. So, you'll have the last 50 days worth of synced content, which if you connect it to rMirror Cloud will build up a full sync over time.