I know silicone for two things: its properties and its ability to harden when still in the tube, before use. Virtually everyone using it knows that after a while, it is necessary to cut the tip to remove the hardened part.
How can I extend its life before application? The number of available silicon types makes them very interesting, if they were usable a couple of years after opening (something basically every liquid glue allows).
Is the hardening happening only on the tip, or also on the back, the part pushed inside with the gun?
Do silicone variants with solvent and the ones without solvent (for example http://www.pattex.nl/dhz/producten/100-procent/100%25%20Universal.html I couldn't find one in English) work and harden the same way? Do they use humidity, light, oxygen, ... to cure?