A model can change after you've already finished building a Lumion scene. Fortunately Lumion can easily update your model with the latest changes, leaving the materials and your Scene intact.
Made in version: Lumion 7.0 Pro.
Knowledge Base: How do you re-import a model?
Knowledge Base: Is there a list of all the keyboard shortcuts in Lumion?
Knowledge Base: How do you update a thumbnail image for an imported model?