I'm also seeing the above behavior. CPU usage reaches 100% after an hour or two. Openfire still responds as expected. Once CPU hits 200%, Openfire stops responding and the service must be restarted. This takes anywhere from 1 to 12 hours.
I've added the IPv4 setting as shown here:
[root@community openfire]# ps -ef | grep java
daemon 7710 1 4 Apr27 ? 00:50:22 /opt/openfire/jre/bin/java -Djava.net.preferIPv4Stack=true -server -DopenfireHome=/opt/openfire -Dopenfire.lib.dir=/opt/openfire/lib -classpath /opt/openfire/lib/startup.jar -jar /opt/openfire/lib/startup.jar
Attached are the relevant files.