RFM - variations

There are some RFM variations that are useful for more specific situations

RFD (Recency, Frequency, Duration) – Duration here is time spent. Particularly useful while analyzing consumer behaviour of viewership/readership/surfing oriented products.
RFE (Recency, Frequency, Engagement) – Engagement can be a composite value based on time spent on page, pages per visit, bounce rate, social media engagement etc. Particularly useful for online businesses.

https://www.putler.com/rfm-analysis/