How important is a deadline for an open post-doc position? I am a last-year phd student, and starting looking for post-docs.

I have seen a very appealing position in a top university, but unfortunately, the application deadline is in the next few days, and I don't have the material time to get the required material (cover letters, CV and so on). 

Nevertheless, the deadline seems not very strict, as they literally say:

Applications will be considered on a continuing basis 
but candidates are encouraged to apply by November 24, 2017.


Now my question: how important is the 24 November deadline (or a deadline ) for an announcement of this kind? Why to put a date if they will continue to take applications even after? Is it common for post-doc opening deadlines to be postponed?
Certainly we can construct scenarios where being late with an application would hurt you, but whether or not it actually does will probably strongly depend on the pool of applicants available.

In all likelihood the soft deadline means "we won't start considering applications until Nov. 24th, but after that point in time we might select and hire someone". If you want to guarantee that you're given a fair assessment it would be wise to have your application in as soon as possible.

If this is really a match-made-in-heaven, and you're confident that you're just as appealing to them as they are to you, it might be worthwhile to send along your CV and a short cover letter explaining why you are really ideal for this position and giving a specific date by which you'll have a complete application submitted.

Note that they're probably only waiting a couple of weeks at most for any stragglers. Don't plan on applying in January.