Many occassions we have seen end users reporting session timed out even though they were working on. This is for sure its an issue from client end and JRE version which client is running on is the culprit for the same. Try to have the same version of JRE which is running on your server or latest one.
Even if this doesn't help try at client end following setting with running JRE:
1. Navigate to: Start > Control Panel > Java > Advanced > Java Plug-in
2. De-select the option "Enable the next-generation Java Plug-in "
3 Restart the browser
4-Retest the issue
Next if you want to increase timeout setting from server end. Do the following:
1. Change profile option ICX: Session Timeout to 60 min from 30, which is default.
2. change s_oc4j_sesstimeout value to 60 again in context file and run adconfig.
3. Bounce the apps services and check.
Happy Troubleshooting !!!