Crashfrog, I agree Adam and Eve were going to die within a thousand years after eating this fruit (2 peter 3:8).
This appears to be the time limit man could live without eating the fruit of the tree of life, not 120 years. After the flood man started living less and less until 80 years was considered a full life.
Adam died at 930 years (kjv genesis 5:5) 70 years short of the end of the day (kjv 2 peter 3:8) that he ate the fruit.