Staggered due dates in Learning Plans

Summary

Is this possible or do I need to suggest an Idea?

Content

We have a new employee learning plan that is currently set for 30 days after it is assigned.  However, we want to add another course to it that is due 90 days after it is assigned.  Is there any way to do this other than to have two separate plans?  We don't have dynamic groups, so can't have a plan that is automatically assigned when the previous one is completed.