[Seven_0]

Once he ate from the tree of Knowledge, then they were forced out of the Garden to prevent them from continuing to eat from the tree of Life.

It is eternal life. One feature of living forever is that you can do it only once. It cannot be temporary and eternal at the same time. If you ever die then you never had eternal life. If you can die then you don't have eternal life.

[ShadowAce]

It is eternal life.

Does Scripture actually say that eating from that Tree once grants eternal life? Or can it be that eating from that Tree extends/renews life?

It's merely described as the Tree of Life. It's properties are actually not described.