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).
Answer. This is a good question as we are all trying to save money however we can. However, there is a very valid reason that contact lens and glasses prescriptions are valid for only a year. This happens so that you will return to your ophthalmologist or optometrist to have a complete eye exam every year.