I previously outlined my patch kit, which is based around Rema patches and vulcanizing cement. Ensuring the health of the vulcanizing cement is key to the functionality of the kit. As with any liquid adhesive, it can dry out in an open tube. Or the tube may sprout a leak, causing the liquid to leak out and vanish. I have taskwarrior tell me to replace the cement in my patch kit every 3 months:
$ task add due:2020-01-01 wait:due-3weeks tag:bike recur:quarterly replace rema vulcanizing cement
The task is really just a queue for me to evaluate the condition of the kit. Because I do not get flats often, there’s a good chance that the cement tube in my kit will be unopened when I perform this evaluation. If the tube is sealed and appears in good condition, I’ll leave it in without replacing it. If it is open, I remove it from the kit and replace it with a new tube. The old cement goes into my toolbox at home. When I apply a patch at home, I’ll first try one these old, retired cement tubes.
Before marking the task as complete, I’ll also evaluate the patches in the kit, replenishing or replacing from my bulk supplies as necessary.
This process gives me extreme confidence that my patch kit will be functional when I need it.