Hermann Ebbinghaus measured this in 1885. The curve hasn't changed.
Spaced repetition is how you bend it.

A dial — not a spreadsheet. One glance tells you how close an idea is to sticking.
Never Forget is fully native. Everything you write — every note, link, rep, and reminder — lives on your devices and, if you choose, in your private iCloud.
No accounts. No servers. No third-party SDKs. We literally cannot read your data.
Everything you save is stored locally on your device. The app works offline — no network connection is required to use it.
Optional sync uses your private CloudKit container. Apple holds the keys; we don't have access. Turn it off any time.
No analytics. No crash reporters. No ads. No trackers. The app makes zero outbound requests in normal use.