Please clarify update procedure for upfront "child themes"

I'm confused regarding your Upfront theme(s). I am very familiar with creating child themes so as not to overwrite changes when a theme is updated. I have installed Upfront and Spirit, a child theme. I see that you are making updates to the Spirit child theme. Do I need to create a child theme of the Spirit child theme (grand-child) so our changes do not get overwritten with updates?