The usage for the word "long"

[W]

First, thanks for viewing this post.

Here is my question: in the sentence "I have long acknowledged this problem...", is the word "long" grammatically correct using in this way?

[Beeesneees]

Hello.

That sentence is correct. It is the equivalent to 'I have acknowledged this problem for a long time.'
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Cheers m' dears!

[W]

Thank you very much.