Data fetching

[drmrbrewer]

When a series of lookups is performed e.g. on Berlin, then Munich, then Koblenz, then Berlin again, how is this handled internally? Is the entire data file for that station fetched each time (presumably the station's kmz file)? If it's up to the user of the library to cache the data locally, is there some sort of expiry or lifetime information associated with the returned data so that we know when to fetch new data?