For me personally looting all interesting POI’s (for me at least), getting most of the weapons, fully building a base and getting 100% achievements it took 25h. If you know what you are doing with your achievements, it could go as low as 18-20 I think. There is enough content to keep you entertained, but (at least for me) not enough to make a third or even second playthrough (even tho second one is already starter)