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).
Your Eyeglass Prescription Expiration After a visit to the eye doctor, you will get a prescription if you need corrective lenses. The prescription will only be valid for a fixed time; eyeglass prescription expiration periods vary but are usually one to two years. The expiration date is the last day that your prescription can legally be used by optical shops and labs to make glasses or provide contact lenses.