I'm not sure how Wizards can track my campaigns to make these kind of declarations. I'm guessing them mean online campaigns similar to their character generators. Seems a bit flawed in their assertions. If I took every campaign (whatever that means) and push them together, that number feels right. I recall starting a campaign when I was in middle school that lasted one night and another that lasted 4-5 nights until someone moved away. I can see where online campaigns might run into the same thing and last only a few nights.
Nowadays, my home campaigns last about 2 years and go to levels 13-15ish before starting a new campaign.