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).
Usually, for a one month pair, it'll be usually about six months per prescription, or six contacts per case. Usually contact lens prescription is good for one year. After the year from when you had your eyes exam, the office or you yourself can make another exam to see if you can still see in your current prescription. 1 person found this useful.