Metamaterials with both reversible deformation and a long load plateau meet the demand for cyclic buffering, offering great application prospects in protective engineering. However, current metamaterials generally suffer from low material utilization, which limits their load-bearing and energy absorption performance. To address these limitations, a novel buffering metamaterial with a long load plateau is proposed in this work. Composed of bilaterally symmetric double-arc structures and vertically symmetric curved plates, the metamaterial is capable of recoverable large deformation and overall cooperative load-bearing deformation, thereby improving material utilization and optimizing structural load capacity and energy absorption performance. Experimental tests and numerical simulations were conducted to validate the long load plateau and recoverable large deformation characteristics of the metamaterial. The influences of structural geometric parameters on its mechanical behavior were also systematically analyzed. The results indicate that the long load plateau can be effectively tuned by adjusting the thickness of lateral double arcs, the thickness of intermediate curved plates, and the central transverse span. Once the intermediate curved plates are removed, the long load plateau feature disappears, and the force-displacement curve presents an approximately linear variation. Finite element simulations at equal mass confirm that the proposed metamaterial possesses better buffering performance than similar structures without a long load plateau, and the underlying buffering mechanism is clarified. The findings provide a novel design strategy for improving the performance of metamaterials with a long load plateau, and facilitate their application in protective engineering.