I used to think it was a good
idea to have an epoxy kit handy for emergencies.
We've had this unopened
container of Loctite's
Plastic Bonder in a drawer for a couple of years now, and when I
went to try to fix Anna's favorite stainless steel pot handle today I
realized it was all dried up.
Not sure what went wrong,
maybe if I stored it in a Mason Jar or Ziplock bag it would still be
fresh and ready to go?
I just pulled out my own epoxy which I had first and last used about 5 years ago. It was still in great condition (and did a great job.) It is also Loctite, but heavy duty - 8fl oz and the bottles are physically separate. I was a bit concerned that the lids would be stuck; no worries though. Maybe the smaller bottles aren't sealed as well?
http://www.homedepot.com/p/Loctite-8-fl-oz-Professional-Job-Size-Epoxy-1365736/100371835?N=5yc1vZc5dkZ1z0t5fs
There should be a either a manufacturing date or a best-before or use-by date printed on the packaging.
The professional epoxies I work with are generally guaranteed for 6 to 12 months after manufacture. And in general, the faster the resin (and 20 minutes at room temperature is quite fast for an epoxy), the less stable it will be.
But I've had resins (that were packaged in sealed metal cans, so protected from oxygen and water) that lasted for at least a decade after their manufacturing date.
Normally the components of these kinds of epoxies are translucent and almost colorless. The colors in your picture are generally indications of environmental degradation. A plastic syringe is not able to prevent that in the long run.