"long before" is correct and can be used in written English. It is usually used to refer to a time in the past that is much earlier than another time in the past. For example, "My grandparents immigrated to the United States long before I was born.".
How long before?
"Those feelings have been there long before".
It was over long before then.
But his contribution began long before then.
It was obsolete long before imperial times.
"It happened long before".
But it had freedom long before that.
Thanks to Ludwig my first paper got accepted! The editor wrote me that my manuscript was well-written
Listya Utami K.
PhD Student in Biology, Bandung Institute of Technology, Indonesia