Have done a few 3ish hour trips (one way) to our cottage with the family. Very comfortable, I don’t think you have anything to worry about. My wife made the comment that it’s nice travelling in style? We had a MY16 V8 dynamic before? I didn’t feel that was a beater lol. But she feels the SVR seats are more comfortable.
On another note, I feel the kids have a bit more leg room in the back too.
I've driven a 2017 SVR From Seattle to Richmond CA fearing the over glorified Recaro seats. Just the opposite. As quirky as they are, they provide excellent surround and lumbar support. They are not quite the Barcalounger found in the living room of a 405 AB L but firm and very comfortable for long distances. I can;t see any drastic changes in seat design for 2018.