when you are addicted to looking at the count down of months/days/hours/minutes/seconds until the release of a long awaited movie/book/game on the website for said movie/book/game in a desperate attempt to make the time till its release go faster.
'Hey Alice'. said Jane. 'are you looking forward to the release of the New Moon movie?' 'Yeah.' said Alice. 'I am! I have major countdownitis, I've been staring at the website for hours!'
(*note. I just used the names of my to favourite twilight characters for the example.)