Multi-Rotor Systems (MRS) present promising opportunities for enhanced energy capture, modularity, and redundancy, but they also introduce unique operation and maintenance (O&M) challenges. With increased component counts, interdependent failure modes, and complex maintenance logistics, effective O&M strategies are critical to ensuring system reliability and cost-effectiveness. This presentation shares key insights from a case study on the O&M of multi-rotor wind turbines at FINO-1 site in the North Sea. Quantitative results are presented to illustrate the impact of maintenance strategies on downtime, availability, and overall lifecycle cost. Building on these findings, the session introduces a startup-developed simulation solution designed to support data-driven decision-making for O&M planning. Developed by Ventarion, the simulation tool (Ventarion Sim) enables scenario analysis and strategy evaluation for both multi-rotor and conventional wind turbine systems. By combining technical analysis, case study results, and applied innovation, the talk bridges the gap between academic research and real-world practice, offering valuable perspectives for researchers, operators, and technology developers seeking to advance wind turbine O&M.