how long?
A couple of things
Last May we bought our cards at the ferry terminal on Lantau using it for both the buses and ferries - recharge at the ferry terminal was not an issue.
BUT when we asked about recovering the card fee and balance the clerk said - you have to go to a MTR terminal to do that... at least not at the ferry terminal.
So the question - how long are the cards valid? We won't be back in HKG until Jan / Feb 2006.....
Happy wandering
WF