How can I remove a Training Offering Due Date in a Learning Plan?

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I'm attempting my first foray into Training Offerings in order to add a new version of a course to a Learning Plan (hate there isn't a better way to do this). When I add the training offering to the LP, it requires a due date, which I can change but cannot remove completely. I'm trying to understand how this will impact our users. This LP is assigned a due date based on hire date, so I don't want the training offering to have a separate due date. Why can't I make it say "N/A" like the courses in the plan?