Everyone is of course different, but for my own experience, as the ride distance got longer I found a few things worked together to make things substantially better.
First, high quality bike shorts. As the ride got longer anything cheaper just didn’t cut it. Stepping up quality levels made a huge difference. Then adding chamois cream to the equation on anything over ~20km multiplied the benefit. Finally, and almost counter intuitively, a padding reduction of the saddle worked wonders for longer rides. Once upon a time when I was riding metric centuries, the most comfortable saddle that I had was a Selle SMP Composit. Zero padding. For longer rides, that piece of shaped hardness was the most comfortable saddle that I had tried. But since those times my riding style has changed and the SMP saddles don’t suit the way I ride any more.