Fetch has the downside that with the usual idea of presence you want to know immediately if presence changes, so you'd be polling constantly. What could make so

Fetch has the downside that with the usual idea of presence you want to know immediately if presence changes, so you'd be polling constantly. What could make some sense is caching server-side and allowing the subscription to be quickly enabled/disabled, so that a client could save traffic while it's not on screen etc. When it returns, it asks for the last message for each contact to be delivered from cache and the subscription to be resumed (in exchange for having to wait for the data to come in, and until then not showing the correct information).