If it is using a similar technology to AirTags, then it could broadcast signal for a long time on remaining battery. Even Bluetooth can do months on coin cell battery.

Moto g30 without cell modem but with enabled WiFi easily gets two weeks of the runtime without much of display time.

My RAZR MAXX could sit for months on the one charge (with already busted battery) without any cell activity.

So if you don't need the display and a hungry wireless tech to keep on constantly you can have enough juice for days, even when the phone is no longer in the power profile to have a full run.