Try putting a nail into the end of the spout before storing the tube.

I the top that I cut off and stick it in backward (little end first. works for a couple of times then it's the nail or even better for me a dry wall screw about 1 1/2 long

What also can work well as a cap is a an electrical connector. You can even try putting a little plastic wrap on the tip before putting on the cap. Of course it will be a large cap you will use.

I put a screw in the end but it pretty much ruins the tip if you want a fine bead in the future.

You can also buy the smaller tubes that are about the size of a tube of toothpaste. Instead of a caulk gun, you just squeeze the tube.

Just for edifacation.(sp) call the company and ask them, I've wasted a lot of $$$$$ with their BS.

Put silicon in freezer to keep it fresh as lone as you want it be fresh. Roll tube from bottom to apply put cap back on soon as you apply. Squessing tube in center will open the end that should be rolled and let air in so go hard from air enter tube only use spout when really needed spread silicone with trigger finger.