Need a maximum time limit and corresponding author-settable message for the quiz. This should be a setting in Preferences > Quizzing > General. It would be great if you could also set a warning time limit and message to warn the learner that time is almost up. For example:

Maximum Quiz Time Limit: 120 minutes
Message: Maximum quiz time has been reached. The quiz is ended.

Quiz Warning Time: 110 minutes
Message: You have 10 minutes remaining to complete the quiz.