Adverbial phrase indicating that an action or state continues over an extended period. Often used with verbs in the ～ている form or past tense.
長いことお待たせしてすみません。
I'm sorry to have kept you waiting for so long.
彼は長いこと入院していた。
He was hospitalized for a long time.
Also means 'for a long time' or 'all along', but is a single adverb, not a phrase. 長いこと emphasizes the length of time more explicitly.
Standard kanji-kana spelling for the adverbial phrase.
Variant using the kanji 事 for こと; less common but seen in some writing.
Uses 永い, which can emphasize a very long or eternal duration; rare in modern usage.
Combination of 永い and 事; very rare.
Phrase composed of the adjective 長い (long) and the nominalizer こと (thing/matter), literally 'a long thing', used adverbially to mean 'for a long time'.