We get attached to some things. Like that screwdriver your dad gave you for your sixth birthday. The handle’s worn and the blade’s chipped, but you just can’t get rid of the thing. If you use this same line of thinking with test leads, it’s a mistake that can get you killed.
Try to make a point of observing the condition of test leads you and your coworkers are using. Chances are, you’ll find at least one set that’s been “repaired” with vinyl tape. What other defects can you spot? The tip that keeps coming apart is an obvious problem, but don’t overlook the fact that the “dirt” on “dirty” test leads may be conductive.
Then, there’s the hidden damage. Test leads that have been walked on, pinched in a gang box, or in some other way subjected to force that the insulation wasn’t designed to handle, are dangerous to use.
Unlike an arc blast, test leads are inexpensive. When test leads are obviously defective, it seems obvious that you should replace them rather than waste time and money “repairing” them with tape that actually does not restore the lead to its rated serviceability. In fact, you should replace them even if you merely suspect they might be damaged.
Test leads are inexpensive, but don’t settle for ones that are cheap. Counterfeiting is a growing problem. Buy a trusted brand (i.e., a company whose meters you use and trust), from a trusted source (e.g., your electrical distributor). This way, you don’t end up with leads that say 1,000V on the package, but actually top out around 300V.
Make sure your new leads are rated for the intended use (e.g., 1,000V, CAT IV), have those finger guards, and have shrouds on the input connectors.