リーダーズ+プラス: throughout - "…の間(ずっと)"
LSD: 〜間ずっと （あいだずっと） (prep) throughout
GG5 (examples: 熊は冬の間ずっと眠っている． Bears sleep right through the winter.
私は宴会の間ずっと台所で....． All through the party I had to stay in the kitchen...
旅行の間ずっと心配していた... Throughout the trip he was worried..
Ngrams: 69k (24k for の間ずっと)

It might be a little obvious, but I'm happy to have it. Since we are calling ずっと as "adv", this can be the same.

@@ -12,0 +12,1 @@
+<pos>&adv;</pos>
@@ -13,0 +14,2 @@
+<gloss>all through</gloss>
+<gloss>right through</gloss>

See below.

Just knocking out "〜". And, also amending the sample sentence to "六時間の勤務の間ずっと" as a better example.

@@ -5,1 +5,1 @@
-<keb>〜間ずっと</keb>
+<keb>間ずっと</keb>

See below.

It is not easy to pick up Google hits because of the combination of "間" with previous kanji. Your [A] link gives a good example of this. The reason I am suggesting this submission is that whereas "間" is usually associated with say "時間" and the like, in this case where the above submission may be preceded by "の"　the reading is likely to be "あいだ". Because the reading rarely crops up except in oral communications it would help the novice to know the reading by having this entry.

In the text which I was reading, it was used as "六時間の間ずっと..."; which I am taking to be "throughout a period of 6 hours".

The following entries are also shown and may be deleted if this submission is accepted.

間ずっと 【？】 (conj) while; down through; during
間ずっと側にいる 【？】 stick around long enough to
間ずっと働く 【？】 work through