When you are in a chat room you can right click in the conversation area and select view logs. One user can only go back a day and another user can view weeks back. Where is the setting to change this?
This is not controlled. Spark will let you go back depending on how much history is saved. Do you think a user might have more history than Spark is allowing to go back? Does it have more history in an xml file with that particular contact?
C:\Users\username\AppData\Roaming\Spark\user\username@servername\transcripts
Although not a Spark feature, Openfire will in the near future be configurable to expose a public HTML endpoint that gives access to chat logs for MUC rooms. Keep an eye out on this issue for the Monitoring plugin, which is used to track the feature request.