Most utility companies installed poles at higher rates during the 1950s, 1960s and 1970s than they have replaced them during the 1980s, 1990s and the current decade. The impact pole age will have on pole performance depends on the percentage of older poles that have been allowed to decay and become weaker. Data from a utility in the Northeast United States found that the pivotal age for poles in its system appears to be 30 years, because the reject rate climbed steeply thereafter.

Durability for a pole plant is defined by the relationships among strength, load and cost. The design criteria used to build pole lines lead to robust, durable performance for many years. But a system with more than 50% of its poles approaching the critical age faces a very different future. Failures and replacement costs are likely to spiral uncontrollably.