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).
Properly fitted, corneal PMMA contact lenses could be worn for 16 hours or longer. Advances in lens manufacturing techniques and fitting expertise among eye doctors led to the mass appeal of these hard plastic contact lenses in the 1950s and 1960s.