As a long term silent reader of this list, I felt compelled to comment on this address expiration topic. I don't believe that address expiration should be part of the protocol. I think instead that the "sending" feature should by default offer guidance to request a fresh address from the recipient. Also allow the receiver of funds to be able to generate an "invoice" that the sender acts on.
I also think that re-directs are fraught with privacy issues. At the end of the day, the ultimate burden is on the sender (with much self interest from the receiver) that the correct address is being used.