I buy a can of Rema vulcanizing fluid and pour it into a small glass vial. I put into the calendar to check the state of the fluid every 6 months. If necessary, I add a solvent. The Rema fluid is usable for about 4 years. Incidentally, I may use it outside of patching, e.g., to glue back together slices of a grip shortened for a handlebar configuration that gets changed. The handlebar rubber is very porous and holds like it was never cut after gluing.