Because most climate controlled storage units are located indoors, there is less chance of outside vermin and pests infiltrating them. Damaging insects such as termites are kept at bay through concrete and metal construction. Unregulated units may become susceptible to outdoor pests such as bees, wasps or mice if not inspected regularly.

Many renters believe that peace of mind is also an advantage. Precious family heirlooms, antiques and other valuable items may or may not survive long-term storage in regular storage units. With a climate controlled storage unit, there is much less chance of discovering significant damage to weather-sensitive items.

Another advantage is atmospheric regulation. Items stored in these units should not face extremes in air temperatures or humidity. Many wood-based furniture pieces, musical instruments and antiques could crack or split from a constant cycle of freezing and thawing. Many storage unit facilities use indirect heating and cooling systems to maintain air temperature, rather than individual heaters or air conditioners in each unit.

Quotings from http://www.wisegeek.com/what-are-the-advantages-of-climate-controlled-storage.htm

Our units are protected by SonEquity Pest Management (http://sonequitypest.com/) which has been serving our area since 1998. They keep our units free from every type of pest, which is a major benefit compared to an outside storage facility that can be overrun by pests such as mice, ants, wasps, etc without proper routine inspections.  Since our storage facilities are located inside of a concrete and steel warehouse termite worries are virtually non-existent. Our units are managed for pest control on a monthly basis decreasing the chances of any pests being in the facility.

Bast also keeps the units at a constant temperature around 70 degrees so your valuables are safe from cold and extreme heat.