Amazon these days is all about Prime. What started out as a way for power users to save on shipping, years ago, has become an all-encompassing membership to the internet’s biggest virtual big-box store. And whatever lever Amazon pushes to get individuals interested in signing up, it works: the longer you subscribe, research finds, the longer you are likely to stick with it.

That’s the finding from a report (PDF) out today from Consumer Intelligence Research Partners.

They’re a retail analytics firm, so they’re looking at two important numbers: conversion and retention. Conversion is all about how many non-paying customers you turn into paying customers; retention is how long you keep those for. Prime, it turns out, is pretty killer at both.

CIRP finds that 73% of consumers who sign up for the 30-day free trial of Prime stay on after that window and become full, paying customers. And once they’re in, they stay in. Consumers who have maintained a Prime subscription for one year (that 73% converted population) are then incredibly likely to stay with it for a second year, with 91% sticking around.

And after that second year, well, you’re pretty much staying. A whopping 96% of Amazon Prime members who make it through their second year then renew for a third.

How many of those Amazon Prime members are there, really? Amazon doesn’t say, but CIRP estimates it’s about 54 million, give or take.

Meanwhile, company just keeps piling on features, and while some of them have problems, backfire, or don’t quite work as intended, it seems clear that the majority of customers like what they’re getting. At least, enough not to bother remembering to cancel.

[via Quartz]

Want more consumer news? Visit our parent organization, Consumer Reports, for the latest on scams, recalls, and other consumer issues.