wrote:
Colin Campbell writes:

I saw a friend riding the other day, and we were discussing what to
carry on a ride.

He mentioned, "A patch kit, and two tubes of glue. One that hasn't
been opened, ..."

And I jumped in, "...and one that has dried out since it was used
for the last repair."

Don't rely on the unopened tube of glue to be any better at no
evaporating. Until the tire patch makers learn that a crimped tube
leaks, we will continue to see completely dry unopened glue tubes.

It's been quite a few years since I last encountered one of those so my
impression is that the makers are getting better at crimping the ends.
I almost always run out of patches well before I'm out of glue, so I
usually put the half-used tube from the previous patch kit into the new
one just in case there should be a leak. More common in my experience
than a poor crimp is an unnoticed crack in the plastic cap that allows
the glue to evaporate.

When closing the glue tube I squeeze it a bit so some excess glue coats
the threads inside the cap. This gives a good seal without needing to
turn the cap on so hard that it's likely to cause a crack to start.