For Pokemon go, it could be once per year:

Aug 2023: https://old.reddit.com/r/TheSilphRoad/comments/1646shv/open_...

Oct 2022: https://pokemongolive.com/en/post/mapupdates-2022/

Pikmin bloom updated once at Feb 2024 after launch at Oct 2021:

https://twitter.com/NianticHelp/status/1760694331466224078