In a recent project, customers (across the board) who purchased new merchandise in their order were 10% more responsive going forward.
Which is a big deal. When I run a Marketing Budget Experiment project, 10% translates to a lot more than 10% over time (due to the compounding interest generated by constantly increasing the size of the customer file).
If you know this fact, how would you (for instance) change your email marketing tactics? You're sending out a daily "blast" ... surely you'd find a way to change two of those five contacts each week to speak about new products that you love, right?