If PAP were offline for a while, or PAP was unable to connect to DMaaP for a while, then a number of messages could have been queued up in DMaaP from the various PDPs.  If PAP were to process all of them, then they could cause PAP to perform lots of work that is ultimately superfluous.  For that matter, it may cause PAP's publishing queue to explode.

Perhaps PAP should discard old messages.  In addition, perhaps PAP should limit the number of messages on its publishing queue. (Is that even possible using policy-endpoints/cambria-client?)