We had the same issue, we discovered that our strophe.js sample code wasn't behaving well (see below), once we used Candy.js (which uses strophe.js) we never experienced the issue. However, since we have no interest in using Candy's UI, we now have to figure out what our old demo client was doing wrong that Candy is doing right.
But at least we have a working model to start with (turning on candy console debug logging helps).
I don't know the details, but it seems the sample code I was using for strophe.js is the issue. It is not with Openfire and/or its BOSH (http-bind) implemenation. As when I use candy-1.7.1.js (which uses strophe.js as its xmpp lib) we are able to maintain length chat sessions without.
Thanks for listening.