With rates at 5%, duration of a 30y bond: 15y, 50y bond: 18y, 100y bond: 20y. In other words you barely get any duration benefit for a 100y bond over a 50y bon

With rates at 5%, duration of a 30y bond: 15y, 50y bond: 18y, 100y bond: 20y. In other words you barely get any duration benefit for a 100y bond over a 50y bond because anything beyond 50y is so heavily discounted it doesn’t matter. There isn’t really any reason to buy that beyond the cool factor.