(be-hav-ior-al de-cay) A new term that describes the rate at which a behaviorally targeted experience becomes irrelevant to the recipient. This rate is affected by the perceived value of the targeted experience, the perceived value of the desired outcome, and the degree of consideration involved with the activity.
When developing a targeting campaign, consider the lifespan you should attach to any given experience. Delivering a targeted experience beyond the user determined expectation for that message is not a positive to the recipient, and very well may be a negative.
Visitor Centric Marketing 
[…] “Behavioral decay” is a term I’ve coined to describe the lifespan that behavioral data maintains from the perspective of the recipient, the end user. That is, consumer actions that are made today will likely be relevant tomorrow but less relevant over time, and at some point will become irrelevant. This is a concept similar to diminishing returns, in that the use of a lever becomes less valuable, in this case, over time. […]