I've no idea why it always downloads the geolocation database every time I start browser, even though it hasn't reached the update time at all?

[nomosaic]

Firefox v139 win10. I set it for monthly.

[tdulcet]

The "Full location" geolocation databases are too large to be stored in the extension's local storage, so they must be downloaded on browser startup. However, the extension requests that they are returned from the browser's cache, so most of the time this should result in no network activity (depending on your browser settings).

If this is a problem for you, I would recommend switching to one of the much smaller "Country only" geolocation databases from the extension's option page. Those are stored in local storage and would guarantee no network activity on browser startup.