I don't have the Steam version so I don't know how many hours I've currently played, but I had the game since January, and I still play it everyday for a few hours. The reasons I play it so much? 1. It's sandbox, so there is no end to the game. I can play for an infinite amount of hours and still not finish it. 2. There is always a new update every couple of months to look forward to and play once it comes out. 3. Rockets, Kerbals, space, and explosions are all awesome!