Never knew these leak too, so heads up on the possibility.
I keep 4 still in shrink wrap in a pouch with a few other bits, which I carry inside my ski jacket. I was preparing stuff for a trip and found two of them leaked tons of brown fluid. Luckily the fluid is still contained in the heat shrink so didn't ruin anything else. The leaking ones are dead, 0.5 volts, but two others seems fine. Interestingly unlike leaking alkaline batteries, the brown fluid seems to be non-corrosive (at least to metal and plastic) and easily wiped off.
They are kept in an outside pocket and being cycled often from -20 to +20, so I guess that eventually broke the seal. The same batch kept in storage are fine.