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).
Disposable soft lenses. Contact lenses were first recognized in 1945 by the American Optometric Association. Over 38 million people wear contacts in the United States alone with international numbers topping 125 million. As more and more people receive proper eye care, the use of contact lenses continues to grow.