1. A method of updating voice prints over time, the method comprising: receiving, by one or more processors, an initial voice print; calculating, by one or more processors, a determining period of time, wherein the determining period of time is a length of time during which an expected degree of change to a subsequent voice print is predicted to occur in comparison to the initial voice print, and wherein the determining period of time is calculated according to an age of a person whose voice provides a basis for the initial voice print; receiving, by one or more processors, a new voice print after the determining period of time; comparing, by one or more processors, the new voice print with the initial voice print; and in response to a change to the new voice print falling within the expected degree of change in comparison to the initial voice print, updating, by one or more processors, a voice print store with the new voice print.