Aaron Oppenheimer posts a nice two-by-two comparing urgency and frequency of product and service encounters. He maps four quadrants for interaction: primary, secondary, auxilary and emergency encounters.
We use this line of thought to understand the difference between […] using a product on day one and […] using it on day 100. It’s a very useful way to characterize the changing nature of interaction with a product, and to give consumers a coherent
experienceencounter no matter when they engage with a device, service, or business.
See also: All Touchpoints, All The Time