The thing of it is is that each time people say "back then", they aren't referring to two years ago or so before each utterance of the phrase. They mean the same time period whether they said it last year or five years ago. I doubt there's a precise division of the years, but I'd say that most consider the golden "Back Then" to be from about a year before the Great Crash of 2001 to about two to three years after the Great Crash. So, let's say the days of messageboard.asp (the united board era) to the end of communitymessageboard2.asp (in the divided board era) or even into maybe communitymessageboard3.asp.

That's just me guessing at the likeliest favorite nostalgic points on our timeline. I'd really be confused if I one day (ten years from now) hear someone say "Hey, remember that second year of RAFO? <singsong voice>Awesome</singsong voice>."