I play GO a lot.
I play it whenever I leave my apartment for anything. I play GO when I walk to the super market, I play GO when I walk to and from work, I play it when I walk my dog, I play it on my free time and during my weekends. I play it with and without friends. I play it in the morning, day and night (I will not eat it on a plane, I will not eat it on a train...).
I have spent sometimes 7-8 hours straight playing this game on my days off. In fact, I played it for so long during an incredibly hot day in the afternoon, that I actually got really sick due to heat exhaustion. It was my own fault (no I'm not going to start a thread blaming Niantic for giving me heat exhaustion... lol), but I just have been having so much fun playing this game that has gotten me to push my body to its physical limits.
I walk everywhere all the time, I'm an energetic guy with a high endurance, Pokemon GO has just turned my normal exercise time into my gaming time. :D