The older I get, the hornier I get......

I like to consider myself a middle aged heterosexual man. I am now in my early sixties but I keep in really good shape and have been told I look younger than I am. I also know that men supposedly hit their sexual peak in their early twenties. Why do I feel more insatiable than ever? I feel like having sex pretty much all day every day. Is there something wrong with me? My cock seems to be hard instantly when I think about sex. My GF loves to do me in the afternoons, but what about at night and in the morning when I am also horny and hard as a rock?