Postdoctoral length before landing a professorship job?
Speaking for Germany: in former times, a "Habilitation" war required for a full professorship - which you usually wrote during your post-doc phase. It usually took about 6 years (of course with strong variations). Now, you can qualify for a full professorship by being a "Junior Professor" - which takes 6 years with an interim evaluation after three years. In some cases, junior-professorships can be transformed to full professorships after six years, but if this really happens depends strongly on your university and faculty (in fact politics says it should be the norm, but in fact universities are having much more junior professorships than full professorships). 

So the general norm in Germany is 6years+, since you usually won't get a position right after your PhD.