We recently bought some soy milk for my 14-month-old son (who had
previously been allergic to both milk and soy, among other things, but
seems to have outgrown the soy allergy!).

We bought WestSoy and the box says it's only good for 5-7 days in the
fridge once it's been opened.  Is this really true?  If so we will be
wasting a lot as he only drinks a bit at once, especially while getting
started.  We have it in a rubbermaid container as the plastic cap broke
off, so maybe that will help?

Are all the brands the same, as far as "fridge-life" goes?  The other boxes
I saw didn't give any indication.

Thanks,
--Robyn