Two-dimensional (2D) hexagonal materials provide a promising platform for valleytronics devices, owing to the convenient generation and manipulation of valley qubits. However, efficient generation of valley information carriers with long valley lifetime is difficult to achieve in single material due to intrinsic valley relaxation channels. Here we show that, such intrinsic limit can be overcome through combining two materials into a van der Waals heterostructure; and report both near-perfect generation efficiency of valley information carriers, as well as record-high valley lifetime. Furthermore, we demonstrate generation, transport, and spatial-temporal imaging of the valley currents in a single device, which opens up new exciting opportunities to realize novel spintronic and valleytronic applications.