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).
More than 30 million people in the U.S. wear contact lenses 1, 2. Two-thirds of contact lens wearers are female 2. The average age of contact lens wearers worldwide is 31 years old 3. Ten percent of contact lens wearers are under 18 years old, 15% are between ages 18-24, 50% are between ages 25-44, and 25% are age 45 or older 2.