One more thing I've noted.

Some manufacturers really have their sh*t together better than others, and it shows. I have had unopened tubes of sealant fail, and in a couple cases I cut them open out of curiosity.

What I found is that the failure inevitably stems from a bad seal or crimp. You can literally see and feel the substance harden starting from a specific point. On metal tubes, it's been the bottom crimp. Poor or worn tooling will create a stress point in the crimp that can cause a seal breach. This is where air and moisture enters, and you can follow the hardened material from that point further into the tube. Plastic squeeze tubes can suffer a similar failure from the heat crimp.

On caulk tubes, the failure is usually at the bottom, the insert that gets pushed in by the caulk gun. Run your finger around the inside of the tube -- if you feel ridges or rough spots, this is where the seal can breach. Often the caulk hardens there and then the tube will no longer be usable -- can't push it in -- even though the majority of the material in the tube is still viable.

I've even had tubes rupture when I tried to push past the cured material. And I've ruined a cheap caulk gun that way.

The all plastic tubes seem more prone to fail than the foil lined cardboard tubes, at least as far as product going bad. It doesn't make sense, those tubes are one piece. But I think the interior surfaces are not as smooth.