If you're very familiar with survival crafting games, 20-40 (generous) hours. Most of that will be hauling back and smithing metal to progress to the next area. Much of the content is simply hauling ore and metals and mining said ores. You will not be doing a lot of combat if you don't go out of your way to find it. If you're easily distracted, enjoy simply relaxing in game, and are a fan of terraforming/building, you can double or triple that pretty easily.