I played Pokemon Sun and Moon for weeks on end at launch. I was insatiable, and its postgame exceeded X and Y to the point where I could be busy for even longer. But eventually a lot of people I know stopped playing, the thrill of trading ceased, and they took too long to announce Marshadow.
I still boot it back up because I love visiting its world, but the Global Missions do very little for me. We're on our sixth one in fact, which asks players to harvest 3,000,000 Poke Beans on Poke Pelago (read; it's just touching the screen and grinding). If you're into these things then have at it! You have from now until May 8, midnight UTC.
Pokemon Sun and Moon [Serebii.net]