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Thanks for the responses.  I received 6 replies:

4 mentioned that they usually freeze the pasta.  One of those said she
accidentally left some out once for several months and it was fine.
Another person said it lasts her a few months no problem.  Karen in
Vancouver had a very bright idea - email the company!  And sent me an
email address.   Thank you Karen!  I wrote to them, and got the info
that in a cool dry place the pasta should last for 3-4 *years*.  I
must say I'm surprised at this, given the oils in brown rice, but I
guess they should know - not that I'm likely to test it out.  :-)

Thanks to all-

Laura