Generic GPS transponder (containing GPS receiver + some kind of data connection) will have limited battery life.

Systems like Tile, AirTag can last much longer with smaller battery and overall dimensions by offloading GPS and long data transmission to other devices. Strength(and dangers) of devices like this is in the size of tracking network not necessarily the hardware itself. Even better if you don't have to plant the tracker onto victim, because victim bought it and is intentionally carrying with themselves.