Some plays are so successful that they run for years on end. 關於這句句子的結構?

Some plays are so successful that they run for years on end.
they run for years on end是副詞子句，修飾前面的形容詞successful（主詞補語），表示「到了這種程度」。

如果寫成
Some plays that run for years on end are successful.
則that run for years on end是修飾名詞plays的限定性質修飾語（屬形容詞性質的子句）。要用關係代名詞that作為子句的主詞。

兩句的句焦點不同（句尾是句焦點）。
有些戲非常成功，可以連著上演好幾年。（受歡迎可以到這樣的程度。語意合理。）
有些連著上演好幾年的戲非常成功。（這話的因果邏輯不嚴謹，不知成功的標準到底是什麼？）

同位語是名詞性質，所以同位語如果是子句時，是「名詞子句」。
The fact that some plays run for years on end is unbelievable.
名詞fact的同位語是後面的that some plays run for years on end.

This is relative clause ;
Used in place of something stated already after the verb "are";Hence so+that;
eg:-Some plays are successful-----so that ----they run (on end) (for years).
eg:-on end=come to an end=finished;
(for years) =a time phrase should be put in the end.

這句是相關副詞so……that使用，that所引導副詞子句修飾前副詞so