I don't have this problem. I take the nozzle off and screw the cap on tightly. There will be a cured slug in the threaded portion of the tube to clear but the rest is still good.
X2. I've had tubes that had to be a couple years old in garage. Temp range -10 to +100, dig the 'slug' out and good to go. They usually don't harden completely till maybe 1/4 tube. Same for most other tube products incl glues, caulk...I've had them where I can't get to come out the end and I cut a hole in side of the tube and get one last use out of it.
