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In my project work, I like to review (at minimum) how many times the customer performs email clicks, site visits, and pages viewed. From a Customer Development standpoint, each "engagement touchpoint" adds to increased response for a short period of time. Engaging on social media might increase response for a day. Engaging via a typical website visit might increase response for two weeks. Engaging via email marketing (click through a campaign - only actions matter, opens are not relevant in my models) might increase response for a month.
If you want to be a master at Customer Development, you'll have programs in place that cause customers to interact with you on a period basis. You essentially become a media brand in addition to e-commerce. It's a prerequisite for success in 2021.