Though they're typically made to last—with a life expectancy between 15 and 25 years—heavy use, poor installation, and electrical surges can negatively impact longevity. Establishing the age of an installation and its components is therefore a crucial safety matter. 15, a junction box is required whenever: You cannot: Common Misunderstanding If a cable passes through without splicing or terminating, you may not need to install a junction box — but you must still protect the conductors according to the wiring method rules. If you do see any visible signs of damage, then it's time to call an electrician (it's illegal in every state to replace these panels without proper certifications). Here's our best estimate of the functional lifespan of each one. Southwire® Industrial Power Cable products do not have a defined shelf life. ) that are designed for many years of service once installed.