After years of experiencing this will all kinds of caulk I looked at a tube I 'sealed' with an end cap on the tip, over top a piece of seran wrap. Then I realized it was the bottom. Take a look at the bottom of a tube. That is definitely NOT an air tight seal. So out came the good old vacuum food saver. That doesn't keep them forever but they are ready the next time I need just 'a dab to do ya". I also use a sharpy and mark on the bag the date the tube was opened. I still have to use that silly rod along side the caulking gun to puncture the tube caulk just as I would if it was new.
Tom, Cheryl & Blossom(coonhound mix)
'05 Winnebago Journey 36G w/Cat. C-7 350 hp Freightliner XC
AFE air filter, aero turbine muffler, 4 FSD Konis, ultra track bell crank and Safe-T-Plus
FMCA 397030
WIT 129107