Why segment at all
Segmentation is what makes lifecycle messaging possible: instead of one message to everyone, you group users so each group gets what's relevant. A new trial and a long-time power user shouldn't get the same email. Good segments turn a list into audiences with a job.
The four categories
Marketing segmentation is conventionally split into four categories. Amplitude lays them out: demographic (who they are), geographic (where they are), psychographic (what they value), and behavioral (what they do). For lifecycle and retention work, behavioral is the most actionable — it reflects real engagement, not just identity.
RFM: a behavioral classic
One durable behavioral model is RFM — Recency, Frequency, and Monetary value. It scores customers on how recently they bought, how often, and how much, then combines the scores into named segments like Champions, At Risk, and Hibernating, each tied to a clear action. RFM is a fast way for a small team to find who to keep, who to win back, and who to reward.
Static vs dynamic segments
A static segment is a fixed snapshot — the people who matched a rule at one moment, like everyone who signed up during a launch. A dynamic segment recomputes as behavior changes: a user joins "active this week" the moment they qualify and drops out when they don't. Dynamic segments are what make journeys responsive; static ones are right for fixed historical cohorts. Neither is universally better — they answer different questions.