What are you trying to do? LEM purges data based on how much is taken up on the appliance. When it gets closer to full it deletes the partitions for the older data all at once. There is no mechanism to delete specific data from what is stored.
If you are talking about syslog files then that is a different story. You can limit the number of syslog files that are kept around and how often they rotate.
You nailed it by stating the appliances limitation. We were wanting to limit what data is saved - by type not by date. As some of our government requirements expect certain logs to be retained longer then others and our backups are massive we were looking for processes to minimize the size of our daily backups and were curious if this was possible.
And as for the syslog's that's not exactly what i was asking about but it is relevant and something i will need to familiarize myself with on our appliance as i was not the one who set these into motion and i do not know the settings pertaining to these.