Given that the circumference of the Earth for a given latitude is easily approximate to cos(latitude) * 40000 km you can fly around 60 degrees north or south and be comfortably on the cruising speed of a 787 (~800 km/h).
At 60 degrees the planet is nearly uninhabited for vast stretches. Ok, that would not affect sunsets. But at 66.6 degrees sunsets stop to happen depending on the time of the year. Already St. Petersburg (Russia) at 60 degrees north is famous for their white nights. At 30.000 ft it's worse. So not convinced about spectacular sunsets, I would expect continuous twilight.
I live at 64 degrees and sunsets take "forever" and are mostly boring compared to at more southerly locations.
I'm aware of that, haha, I live nowadays right by the 60N latitude (Stockholm, Sweden) and came from Brazil at around 23S, I've experienced both types of sunsets and I'd say I find the ones at higher latitudes to be much more spectacular than the short ones closer to the equator.
So let's say a trip onboard a 787 around the +-60 latitude during spring/fall equinox is completely doable for chasing the sunset :)
I live at 64 degrees and sunsets take "forever" and are mostly boring compared to at more southerly locations.