For the 2009 the only reason we got a teaser so early is because it was released before Paramount decided that the film should be shown in the Summer and not Christmas break. Otherwise we would have had to wait another 6 months for that teaser.
The teaser for the last one came out 11 months before the movie was scheduled to be released at the time. For this one that would have been July. I now think however that it will probably come out in November.