There's a distinction to be made between dying and death. It's not all uninterrupted dying. If one's healthy and feeling well, it's invisible dying. The end that is a certainty is not necessarily boldly announced. No, you can't understand. The only thing you understand about the old when you're not old is that they have been stamped by their time. But understanding only that freezes them in their time, and so amounts to no understanding at all. To those not yet old, being old means you've been. But being old also means that despite, in addition to, and in excess of your beenness, you still are. Your beenness is very much alive. You still are, and one is as haunted by the still-being and its fullness as by the having-already-been, by the pastness. Think of old age this way: it's just an everyday fact that one's life is at stake. One cannot evade knowing what shortly awaits one. The silence that will surround one forever. Otherwise it's all the same. Otherwise one is immortal for as long as one lives."
I have to admit to having read only one book by Philip Roth which I didn't like all that much. Very didactic. Can't even remember the name of it, but it was published in the last six or seven years.