I don't think the time really matters. Most people have a hard time keeping quiet for two minutes anyway. I think the extra time may be because September 11 2001 is fresher in people's heads. It's more raw, and most of us can remember the exact moments it happened. Many of us knew someone, or have friends that knew someone.

I recently met Terry Kelly. He has a CD out - The Power of the Dream, which has a song on it called 'A Pittance of Time'.