The Iron Rule of RFM

For FREQUENCY, rather than coding by individual lifetime order count (which again would require too many codes), we usually create just two groups: one-time buyers and multi-buyers.

Why not assign different codes to three-time buyers, four-time buyers, five-time buyers and so on? Larger catalogers do this, but the major difference in response comes between one-time buyers (who may only be testing you out, and may yet be disappointed by what they receive), and multi-buyers (who have come back at least once, proving that they really are satisfied.) So smaller catalogers often opt for the greater simplicity of just two frequency groups.