Ian Eames of University College London has developed a math model that can predict how time will ravage that pretty picture on your chest/bicep/penis/etc. You see, the chemicals used in tattoo ink degrade as the canvas of skin they're stabbed into degrade—cells split, die, and shed. As the cells go, so goes the ink.
Eames' conclusion? If you're looking for longevity, his model points to simplicity:
Broadly speaking, what my paper shows is that the small details in a tattoo are lost first, with thicker lines being less affected. Although finely detailed tattoos might look good when they are first done, they tend to lose their definition after 15 years - depending on how fine the lines are
So instead of the tattoo of you and your girlfriend fending off a fleet of Napoleonic galleons with an ion cannon, surrounded by the lyrics of All of the Lights in cursive script, maybe just go with "TRICIA" or a hexagon. [New Scientist via Mathematics Today]