We report for the first time the laser-printer-based fabrication of vapor- and pressure-resistant microfluidic single-use valves and their implementation on a centrifugal microfluidic "lab-on-a-disc platform". As an extension of this technology, we implemented long-term storage of liquids for up to one month with no signs of evaporation. This simple technology is compatible with a range of polymer microfabrication technologies and should facilitate the design and fabrication of fully integrated and automated lab-on-a-chip cartridges that require pressure-resistant valves or long-term reagent storage.