Hello,
The default session length in epesi is dependent on server configuration, from what I've seen 24 minutes being the most popular setting.
You can change that, for each user separately of as an admin - set new default for all users.
The setting is available in Menu->My Settings->Control Panel->Misc, Keep session at least (change to 24 hours). If you want to set it for all users, go to Admin->Default User Settings->Misc, Keep session at least.
I believe this should resolve your issue.
Kind regards,
Arek