Postdoctoral length before landing a professorship job? professorship: tenure-track position, or "good" assistant professorship. Basically, a position that upgrades the postdoc status, and gives a much higher chance of a future permanent position.

I'm currently going to start a postdoc in applied mathematics and I wish to land a permanent position at some point in my life. Naturally, the situation seems dire, and albeit I'm highly confident of my skills, one never knows. 

So, my plan is to fix a deadline time to do my best, and if I don't get a professorship by that time, I should start, without a question, to seek for a job at the industry. 

The natural question arises, which is this optimal stopping time? According to my advisor, I should land a professorship in 3 years, but I'm not sure if this is true. 

So my question to academia.stackexchange: What is, in your experience, the postdoctoral length of a freshly hired professor at your institutions?

For sure my question is highly dependent on country and research area, I would appreciate answers for my specific case (Germanic world, Applied mathematics), but I think the presented answers could be meaningful for a lot of other fellow postdocs.

For what is worth, I would love some sort of database on newly hired professors, as it would also make possible to compare "strengths". But I've briefly scanned the internet with no positive results.
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.