Perfectly normal. The whole point of sessions is to be able to associated data from one request with data in another request. When you let the session for some request expire, you are saying that that request's data shouldn't have anything to do with any future request.
More specifically, the flash data is a part of the session data -- see the _save_flash
method in the Catalyst/Plugin/Session.pm
file, for instance. Also see the big warning for the delete_session
method:
NOTE: This method will also delete your flash data.
How to cope with it? You need to persist data from a request using any scheme other than the Session plugin. Without knowing more about your app, what data you are trying to persist, and how you will associate data from an old session with a new request, I couldn't begin to make a more specific recommendation than that.