When you say "all falls down", I'm not sure what that means. Is the app erroring out? Just guessing here, but if you are using long-running conversations to maintain state (probably), then you may be experiencing a conversation-timeout. You can set the conversation timeout through the <core:manager conversation-timeout="...">. You can also redirect to a no-conversation-view-id if the conversation times out.
Maybe the way is to set <core:manager conversation-timeout="...">
but, how can I set no timeout? or disable it?
conversation-timeout= -1 ??