It lasts six months at room temperature, but ~18 months in the refrigerator[1] (I have seen claims you can double that in the freezer, but haven't tried).

1: https://en.wikipedia.org/wiki/Sugru#Properties

I've ordered a 20ish pack every couple years since the Kickstarter and I always immediately put it all in the fridge. I usually have a few packets go over the expiration and I must agree, ~18 months is when it starts to dry out and become brittle and thus not work as effectively. Using a bit of water combined with lots of massaging helps but detailed work is no longer possible (like building replacement handles for little coffee cups).

I've been using FormCard as a replacement in a lot of places (lately custom-made "hangers" with screws to hold my router from the wall), since if I mess up or I want to recycle it, I can just drop it in boiling water to melt and start over. Although I must admit, Sugru feels much nicer and is a bit softer i.e. good for cushioning - FormCard solidifies after 3-5 minutes into hard, slippery plastic which e.g. doesn't work very well for coffee cup handles or drop-protection for sensitive equipment (phones, cameras, etc.).

That is way better. I hadn't thought of refrigerating it... at the same time I want it in my toolbox and I've got kids so my refrigerator is a mess as it is ;)

I do appreciate the info though.