Long-term monitoring of the ocean, for instance its seismic activity, remains a technical and a financial challenge. Despite technological advances in reducing the size and consumption of electronic components, in providing powerful energy through Lithium batteries, and in reducing the size of sensors, the new generation of stand-alone instruments such as Ocean Bottom Seismometers (OBS) cannot be deployed on average for more than a year on the seafloor and provide access to their data only upon their recovery. Any long-term monitoring thus implies multiple cruises and redeployments. Permanent observatories with real-time access to data require ambitious cabled-to-shore sensors and infrastructures. Here we propose an alternative solution bridging the gap between these two end-members, consisting of multi-parameter platforms for seafloor (MUG-OBS) or water-column (HYDROBS) observations, and offering a lifespan of four years and an access to the collected data through data-shuttles releasable on demand from a surface ship.