What is most interesting to consider about the 120-year age limit is not what is found in old testament genealogies and chronologies. Go look at the world around you. Who is the oldest person in the world at this time? Who is the oldest person upon death in modern times? Here is a quick link to get started if you wish (no, not authoritative of course):
Oldest people - Wikipedia
The Genesis account was written approx. 3,000 years ago. We live in a very different world now. People are living longer than at any point in history since the early Genesis records. And yet, one person is listed as having lived past 120 (if you really, really want to count 122 as *past* "120 years"). What is more interesting is that the one who lived this long (and I think birth records from this far back could be in dispute) was in fact not a "man," whom God said he would not contend with forever, but a "woman." The oldest man found on the list is *disputed* as having lived 120 years...probably less. This is all very interesting to me.
™ Version 4.2