A major inhibitor of the effectiveness of security warnings is habituation: decreased response to a repeated warning. Although habituation develops over time, previous studies have examined habituation and possible solutions to its effects only within a single experimental session, providing an incomplete view of the problem. To address this gap, we conducted a longitudinal experiment that examines how habituation develops over the course of a five-day workweek and how polymorphic warnings decrease habituation. We measured habituation using two complementary methods simultaneously: functional magnetic resonance imaging (fMRI) and eye tracking.