Copper trolling wire is a great tool for targeting suspended fish away from the boat. However, wire of any kind, particularly copper wire, was never designed to be submerged under water and constantly wound and unwound onto a small diameter fishing reel under any kind of tension. Even plated super copper eventually becomes stressed from these conditions, not to mention damage to the wire and eventually it must be repaired or replaced.
Once super copper (silver colored) becomes extensively grey-ish colored (usually after 1.5 seasons of continuous use) it is time to think about replacement. The individual strands become brittle and are more susceptible to breakage under tension.
If the copper wire is relatively new and still maintains a soft and flexible texture and you have a broken strand or strand separation occurring, then it's time to perform a copper repair.
Simply cut the effected area and overlap the two tag ends. Pinch together in the middle and twist the tag ends back up the mainline about 8-10 times and trim. This repair is stronger than the original wire.
If you like, it is possible to slide a small section of heatshrink on one of the mainlines before performing the repair, and the sliding the heatshrink down over the repaired area and heat. This will protect the repair area from tag ends catching on line guides and other objects.
Copper trolling wire does not last forever, it does not actually have 32lb or 45lb or 60lb of tensile strength....it is only in the mid 20lb range for most "30-40lb" copper. As mentioned many times before, those ratings are for diameter equivalent in monofilament only...for reel fill purposes.
Pay attention to damages from tangles, line guides, excessive tension, wet storage, strand separation and kinks periodically and perform repairs or replacement when necessary.