In general , after discussion with a few of my co-workers , you can turn off the flow if its sitting for a few days. I would turn it back on an hour or so before use. If you need more information, please feel free to respond with the model of GCMSD and we may be able to be more specific.
James is correct It is crucial also not to disconnect the SS tubing from the regulator. You do not want any moisture to collect in it.