I'm assuming that you're doing direct client to client connections for this (eg, link local, etc)? Otherwise the server should ensure that the presence is kept up to date.
There is also the new XEP-0334 for processing hints that could be expanded, and it might be a good fit for this: <presence from="alice" to="bob"> <ttl xmlns="urn:xmpp:hints" seconds="600" /> </presence> or <presence from="alice" to="bob"> <expires xmlns="urn:xmpp:hints" stamp="1969-07-21T02:56:15Z" /> </presence> -- Lance
smime.p7s
Description: S/MIME cryptographic signature
