For any given substance, the heat capacity of a body is directly proportional to the amount of substance it contains (measured in terms of mass or moles or volume). Doubling the amount of substance in a body doubles its heat capacity, etc.
Conventional soft contacts can last up to a year; conventional rigid gas permeable (RGP) contact lenses can last even longer. Frequent or planned replacement contact lenses last one to several months. Disposable contacts last from one day (daily wear) to up to two weeks (extended wear).
A contact lens, or simply contact, is a thin lens placed directly on the surface of the eye. Contact lenses are considered medical devices and can be worn to correct vision, or for cosmetic or therapeutic reasons. In 2004, it was estimated that 125 million people (2%) use contact lenses worldwide, including 28 to 38 million in the United States.