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).
Though PMMA hard lenses were not gas-permeable, they were fitted so they could move with each blink, so oxygen-carrying tears could be pumped under the lens to keep the cornea healthy. Properly fitted, corneal PMMA contact lenses could be worn for 16 hours or longer.