I think I could probably play The Witcher 3 forever. Honestly, I'm starting to think I have a problem because I have been playing this game since February and I am not sick of it yet. I usually get sick of open world games after a few weeks and end up finishing them a year later when the fatigue has worn off. Yet, with The Witcher 3, I think about this game when I'm not playing it and when I play it, its hard to tear me away. I have to put myself to bed when I play it in the week and have to work in the morning.
Of course, the game isn't perfect and it is possible that next week I will be sick of it. But at the moment I could play this game forever, no other game is getting a look in.