[fwdude]

"Adam could very well have been in the Garden for a billion years."

Excellent point.

Although you would have to disbelieve the Bible to believe that (which is what this piece argues):

Genesis 5:3-5 (NIV):
"When Adam had lived 130 years, he had a son in his own likeness, in his own image; and he named him Seth. After Seth was born, Adam lived 800 years and had other sons and daughters. Altogether, Adam live 930 years, and then he died."

[Hostage]

The question is from what point did he live, from his creation or from his expulsion? An argument can be made for either.

He was immortal and then became mortal. Years of age would seem irrelevant to an immortal being.

The Genesis passage you quote does not settle the question.

[Psalm 73]

"Altogether, Adam lived 930 years, and then he died..."

Starting from the "Fall", or starting from his creation?