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.