Originally Posted by
9Benua
Once I updated, how long will they keep it stored on my smartphone locally?
That depends on what you've set on your phone. On iOS devices for example you can tell it to keep all calendar events, regardless of age.
It is an iCal feed - the device downloads it, stores it as a calendar and then TripIt has nothing more to do with it until new events arrive, which it adds to the feed.