Pressure swing adsorption (PSA) assemblies with optimized startup times, as well as to hydrogen-generation assemblies and/or fuel cell systems containing the same, and methods of operating the same. Startup and shutdown methods for a PSA assembly, and optionally an associated fuel processing system, are disclosed to provide for shortened startup times. The PSA assemblies may be in fluid communication with a hydrogen source that may be used or otherwise configured or controlled to purge the PSA adsorbent columns of adsorbents during startup and/or shutdown procedures, the hydrogen source additionally or alternatively may be used or otherwise configured or controlled to charge the columns with hydrogen for idling in a pressurized state. The use of this hydrogen source, together with specific startup and shutdown methodologies, provides for reducing the startup time of the PSA assembly.