Bogart,
This problem would be solved if your students save their answers more often. Each time they select the Save without submitting button, the session handling timer would be reset and then they should have no problem compeleting the quiz.
You can help them do this by not only asking them to save periodically, but you could also limit the questions per page (we usually recommend to our faculty 10-20 questions per page). This way that after every 10-20 questions, they (students) will see the Save without submitting button and will select it before jumping to the next page of questions. This also helps save their answers up to that point in case they experience technical difficulties (loss of internet connectivity, power outage, etc.) The students then have something to continue instead of having to start all over again.
In regards to changing the coding to extend the session handling time limit, you will have to wait for someone else to respond as I don't have access to the backend of my system.
