"have been forever" is a correct and usable phrase in written English.
It is often used to emphasize the continuity and longevity of something. For example, "My love for you has been forever."
Our lives have been forever enriched by her presence.
Legal battles are being waged, and residents' lives have been forever changed.
Only a fool would conclude that News Corporation's designs on BSkyB have been forever abandoned.
For earlier generations it may have been Forever Amber or Peyton Place.
They, too, are wounded, and their lives of selfless service have been forever marred.
If they had gone on to win, their winner's single would have been Forever Young.
DT Alan Branch He may have been forever stigmatized as an underachiever after his lackluster time in Arizona.
"No human being could have come through such a World War I-style conflict and not have been forever affected.
Though our lives have been forever enriched by his music, his ebullient spirit will be sorely missed.
This ruling will finally give justice to those whose lives have been forever changed by these military criminals.
They take, I suppose, a Cuban view, that matters on the island are perpetually and in some way inherently screwed up and have been forever.
