when you no longer feel like you have to keep up with pop-culture. nor could if you wanted to. (i think that's pretty much the defining moment right there).
When you look at the Rolling Stone's list of the top 50 songs and you realize you've only heard 3 of them.
When on a list of perspective women, the only ones you find of any genuine interest of any sort of lasting relationship with seem to all be over 35. Maybe not so strange were your name harold and you had a cool assed e-jag converted into a hearse. Maybe I'll let the fact I still want that car make me feel young again.
when you stop at the stairs ...see some ice and spend 2 minutes figuring out the safest route to take