Your spouse/boss/dog asks you "When is it exactly you'll be gone for AN ENTIRE WEEK?"
Your appointment book for October 15-19th starts looking like a schedule for the trains leaving the Frankfurt Hauptbahnhof: One every 15 minutes.
Your email program, suddenly inundated with emails from publishers in China, Russia, Hungary, South Africa, India, and starts filing everything as SPAM.
You're assistant/travel agent calls to tell you that your favorite hotel is booked up, but they've found you a "very convenient one just a half hour train ride outside the city."
You draw up various lists of people: Those you want to have appointments with, those you want avoid having appointments with, those you want to have a drink with, those you want to...
Your colleagues start making excuses about why they aren't going to Frankfurt, complaining that "the exchange rate is just so terrible," while secretly wondering what they might miss and wondering if they should reconsider.
You start dreaming of a quick jaunt down to your favorite small hotel in Italy/Greece/Spain for a few days right after the Fair is over and wonder if anyone would miss you...
Tell us, how do you know it's time for Frankfurt?