If you're going to use silicone, then do yourselves a favour and use
Kop-R-Lastic caulk instead:



It's as water resistant as silicone, but it sticks to itself better than it sticks to other materials, and so if you ever want to replace it, you just get it started and it pulls cleanly off every material I've ever put it on. So, if you ever want to replace the stuff, removing it completely is easy. Removing silicone caulk completely is like fighting with a bear. Here's a picture of me pulling fully cured Kop-R-Lasti off of Suite 3's dining room window:



Note how cleanly it pulls off the white PVC window flashings.

If you can't find Kop-R-Lastic being sold locally, check your local hardware stores (especially the evestroughing section of Home Depot) for "Stone Mason Gutter & Siding Sealant":



It's exactly the same stuff as Kop-R-Lastic being sold under a different name.

This synthetic rubber cures by reacting with the humidity in the air. So, to store a partially used tube, just candy cane a bit out the nozzle and put in in the freezer. It'll keep for an awful long time that way cuz the humidity of very cold air is extremely low AND the cold temperatures minimize the rate at which that chemical reaction that causes the rubber to cure takes place. When you're ready to use the tube again, just put it in your caulking gun, apply some stiff pressure, pull the cured plug out the end of the nozzle, and it should slowly start flowing again. Allow time for it to warm up before using it. You can candy cane it overnight, or even for several days.