“长久以来“怎莫用英文说

a long time since...
He has stayed in that city for a long time since he left hometown.
自从离开家乡，他长久以来都住在那个城市。

since a long time ago

For a long time
Since a long time ago

FOR A LONG TIME

Since long-time
或者
Long time ago

Long long ago,
For a long time,