Hi Baudrunner, I actually have a theory on the biblical life span amount of time.
The earth spun faster then, so a day was equal to 3.42 hours. I have this written out somewhere on the net, I'll find it and copy and past it. I figured it with a beginning at 6,000 years ago (the mountains weren't as high so there was not so much spin lag), and I also figured the first 7 days to amount to a few million (in our current time understanding). Gosh, I think about so many things and right now I can't remember how I came up with the math except that I divided 7 days into 24 hours and the 2 middle days (tuesday and wednesday or thursday), were equal days. They took the longest to create and were more like one big day.
So with time slowing down, we really don't know how old we are.
I'll find it if you are interested. But it might be too simple that it confuses people.