sorry for the below information, i have not tested though , it says it's in seconds, so set 24 *60*60 ( 1 day) and observe if it logsout after a day..
To set password rules for reporting user accounts
1 Select the reporting server and make sure you are logged in.
2 On the Admin tab, click GUI Configuration > Password Rules.
3 In the Rules for role list box, select the role.
4 Change any of the parameters for the password rules.the parameter here being "Inactivity timeout"
5 Click Save to save the rules for the selected role.
hope the information helps,