Post #551799 by GatorRob on Thu, Sep 2, 2010 4:04 PM

By "plastic bottle", I take it that it's a commercial brand? Here is what I can tell you Sonoma syrups (good quality, highly recommended, but somewhat high price) told me about the shelf life of their products some time ago:

Our product is shelf stable without refrigeration because of its density and
because we add ascorbic acid, a natural preservative. If you refrigerate
our syrups they get clumpy much like honey when it is refrigerated. Once
open we suggest the product be used within 6 months. We have found that it
is around that time the infusion starts to loose its intensity.

So, it's likely your orgeat won't go "bad" for a very long time, but it will lose some flavor over time.