Is the date of final compilation of the books of the Old Testament an integral feature of the Wellhausen Documentary Hypothesis? So, using the Wellhausen Documentary Hypothesis scholars argue the books of the OT are finally compiled much later than the "Traditional" view.  Are the dates for the final edition critical to the theory? 

I accept this is a difficult question because for the last 40 or 50 years proponents of the Hypothesis have splintered into various groupings with differing variations to the theory.  I am not familiar with these splinterings, various alternative models, so maybe someone could summarise the variations as well.

It would be good to see what are the majority opinions about the date of the final redaction/compilation of all the OT books, in the various main modern offshoots of the Documentary Hypothesis.
Before we dive into the various hypothesis models, it it useful to list the points that all these models (and the wider academic historical circle) are in agreement on:


the Torah/Pentateuch is not a unified work from a single author, but is made up of sources combined over many centuries by many hands. 
the Pentateuch was not dictated to Mozes
it is the product of a long evolutionary process
redaction/compilation was done by several individuals over a long period of time


The disagreement over the models is solely focused on: 


the dating of the redaction and compilation moments, and
the number of sources involved in redaction and compilation


The main models with varying sources are usually illustrated by this combined diagram:



And for most of these components we have fairly accurate dates:


J: Yahwist (10th–9th century BCE)
E: Elohist (9th century BCE)
Dtr1: early (7th century BCE) Deuteronomist historian
Dtr2: later (6th century BCE) Deuteronomist historian
P*: Priestly (6th–5th century BCE)
D†: Deuteronomist
R: redactor
DH: Deuteronomistic history (books of Joshua, Judges, Samuel, Kings)


So if your question is "when was the most recent redaction/compilation done?" it could not have been earlier than the dates for the used components. So, for example, if you follow the D† argumentation, the last redaction could not have been before the 5th century BCE.

Modern scholars generally see the completed Torah as a product of the time of the Persian Achaemenid Empire (probably 450–350 BCE), although some would place its production in the Hellenistic period (333–164 BCE), after the conquests of Alexander the Great.

Poetics and Interpretation of Biblical Narrative
By Adele Berlin



Egypt on the Pentateuch's Ideological Map