if you search the forum on same topic....you will see a number of discourses on the topic over the years.

fwiw....my personal perspective is that i do a couple test batchs on old stuff and if it works (e.g., fully hardens), i use it.  i have certainly successfully used epoxy older than a year with no apparent problems.   current boat i am building....all the epoxy (resin and hardener) is over three years old and no problems what so ever.

that said, i know it's not what the manufacturer recommends....but i have never heard them say that if the old stuff fully cures...it is somehow inferior to fully cured newer stuff.

h 

I talked to the guys at the MAS booth in Port Townsend this year about this very thing.  My kit is a year old and he said it'll be fine.  Making a test batch is always a good idea though...

   I've got stuff ( US Composites ) that is now 7 years old and is still working as it did when I first purchased it...

  < I've got stuff ( US Composites ) that is now 7 years old and is still working as it did when I first purchased it...>

You either bought a heck of a lot of epoxy or you're not doing enough boat building!  :)

I've used ten-year-old epoxy without issues. Always make up a small test-batch if in question!

The shelf-life seems to be indefinite at room temperature. The one thing that seems to kill epoxy (of any brand) is being stored at cold temperatures.  

I had a thousand-dollar unit of hardener that spent a winter frozen solid in Maine, and nothing I did with it ever cured. There's a half-finished nesting dinghy up in the attic here at CLC that got started with that batch...

Keep your epoxy at comfortable room temperature at all times.  IE, 60 degrees F and above.

Good time to revisit this 15-year-old post, which is still absolutely relevant:

Epoxy and Cold Weather

Thanks all.  The epoxy was fine after 6 mo in storage (in an 84 degree house in Florida).  But the hardener pump was kaput.  Thought I'd cleaned it out good before we left.  Oh well.  I can measure.

Got the hull-deck joints in the fore and aft sections on the one side that remained filletted and taped and also filletted the bulkheads to the deck.  So now I need to spend a couple of hours sanding everything smooth and rounding off edges in preparation for glassing the outside.  This last little bit of work used up the last of the original big jug of resin.  The kit came with a second smaller jug.  Hope I've got enough hardener to get through...