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).
Photochromic lenses last as long as your prescription. Plastic photochromic lenses usually out last the lifetime of a patientâs prescription, about 2.5 years. Glass photochromic lenses never stop working; in fact glass Photochromics get better with age and will not slow down or loose the darkening ability.lastic photochromic lenses usually out last the lifetime of a patientâs prescription, about 2.5 years. Glass photochromic lenses never stop working; in fact glass Photochromics get better with age and will not slow down or loose the darkening ability.