Multiple rounds of "continuing action" conjugations

Question

I got this question from a JPLT quiz app:-

ドラマを見つづけていたら、朝になってしまいました

I'm guessing it means "As I was watching the drama, it became morning", but noticed both clauses go through the "continuing action" conjugation multiple times. Wouldn't a simpler way of saying that be:-

ドラマを見つづけたら、朝になりました

What other nuances are being implied here?

Answer 1

ドラマを見つづけていたら、朝になってしまいました。

The ～ていたら indicates that something happened while you're doing the action, meaning "while I was doing~~", and ～てしまいました indicates an unintended result or the speaker's regret.

Examples:

• テレビを見ていたら、電話が鳴った。
  While I was watching TV, the phone rang.
• ガラスを割ってしまいました。/ ガラスが割れてしまいました。
  I (unintentionally) broke the glass. / The glass broke (and I feel sorry about it).

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ドラマを見つづけたら、朝になりました。

This sentence has lost both of the meanings/nuances of "while I was doing~~" and "unintended result or regret". And ドラマを見つづけたら part sounds a little unnatural to me, because it sounds like "When/As I continued watching dramas, morning came", "I continued watching dramas, and because of that / as a result of that, morning came."

Example:

• 触ったら、壊れました。
  I touched it, and (because of that,) it broke.
• Cf: 触っていたら、壊れました。
  While I was touching it, it broke.

Answer 2

Same difference as "While I continued to watch the drama..." and "While I was continuing to watch the drama..." I suppose.