In fact, it turned 15 years old this past April[3].
[1] https://www.rsync.net/resources/notices/canary.txt
[2] https://en.wikipedia.org/wiki/Warrant_canary#Usage
[3] https://twitter.com/rsyncnet/status/1387090538273206274
https://www.rsync.net/resources/regulatory/privacy.html
I was referring to Protonmail's canary specifically, in the event that wasn't clear.