I agree that 10 years is a little short, but I wouldn't call it absurd, certainly not comparable with the absurdity of 95 years. When you speak of GRR Martin "losing ownership" of his characters, ownership wouldn't simply pass to HBO, it would pass to everyone. So HBO would have exclusive rights over their specific adaptation of the story, but they wouldn't have exclusive rights to Jon Snow and Daenerys Targaryen as characters. A lot of us think that there would be a real social benefit to popular characters belonging to everyone, not just their creators. In any case, a 10 year copyright term would fundamentally change the dynamic

I think 30 years would be a reasonable medium. A writer who publishes a novel at age 20 could profit until she's 50. And most writers are active at older ages anyway, so this should be plenty of time. And certainly no movie or TV studio executive is actually thinking of profits 30 years down the road when they begin a project today.