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).
One to two years. Powdered products, such as eye shadow, blush and face powder can last longer â up to three or more years. But those guidelines depend on how sloppily you use the products (see below). If you don't know when you bought a product, you can gauge its safety with a critical sniff `n' look.