I always got the impresssion that with "re-negotiating" his contract he got his freedom yes, but lost his immortality as well. So IMHO he lived a full lfe but died a bit over 1000 years ago.
I have done my research on this topic before making this post to be sure. The wiki is misleading in this regard, stating the same thing you say. But that's just a synopsis of his backstory, and doesn't spoil how his story ends.
In game it is specified that he gained immortality from a demon, but with the catch that the demon would come to claim his soul in 1,000 years. But he learned he could get rid of that part and just be immortal if he manages to kill the demon, which you do.
"This thousand year limit is but artifice, and of your making!"
So we have the perfect making for a recurring character despite it being thousands of years later, so it's my one hope that the game will deliver in that regard.