Recently, we talked about customers who return a lot of merchandise. Stop mailing them!!
If you agree with that premise, then take a look at customers who predominantly purchase during the Holiday Season, as an example.
Once a customer purchases for the third time, habits set in. If the customer purchased during the Holiday Season during 2009, 2010, and 2011, then take a careful look at what the customer does from mid-January to mid-September in 2012. Run a profit and loss statement for this eight month period of time. If the profit and loss statement doesn't look favorable, stop marketing to seasonal buyers ... except for the season when the customer purchases!