For MotherNature.com, the stream of contribution margin (the return side of ROMI) is defined by the lifetime of repeat sales generated by a satisfied customer. This implies computing the CLTV, which assesses the value of a customer as an asset in terms of the future net income from that customer. Thus, CLTV models include terms such as average order size, gross margins, order frequency, retention rates, and the expected duration of the customer relationship.