If life is suffering, extended life is extended suffering. If life is joy, extended life is extended joy. Defeating death solves only one problem: death. So long as there is life, it is up to the one living it to make the best of their hand. The task never ends, however long that life may extend. There is no "if only [whatever] then everything would be wonderful and there would be no more problems ever."
The only lesson I draw from Sedaris' pitiful story (I have only read the notes, not listened to the interview) is that at any time once he was grown up enough to be able to knock his father down he could have solved the relationship by ignoring him. That's what he did with his sister, after all, and the denouement of that was only that he was a bit sad she committed suicide. How can someone be 60 years old and still be "in the shadow of their father"?
I'm with J.K. Rowling here: "There is an expiry date on blaming your parents for steering you in the wrong direction; the moment you are old enough to take the wheel, responsibility lies with you." If someone is young and full of energy for centuries, and still burning up with resentment, it's a self-inflicted problem that they could let go of at any moment.
First, I must state, for the record, that I am personally all for eternal youth for anyone, for as long as they want to. (By "eternal" I mean somewhat less than infinity, maybe a few hundred years to start.)
That said, I have been listening to an interview with David Sedaris on NPR, who lived to his 60s in the shadow of his abusive father, and the reprieve came only when the father got old and demented, and eventually died. We usually talk about highly visible cases, where, say, tyrants and dictators do not give up control of, say, a country. But the real (aggregated) suffering is at much lower levels, where the torture, physical or emotional is mostly hidden and personal. Unless you are a negative utilitarian, this suffering probably does not outweigh the benefits of feeling young and full of energy for centuries, but it is still a lot of suffering with no recourse, and often with little to no visibility. I am not sure how to feel about this worse-than-Omelas possibility.