Working with something already in my head, about 2k words is typical before I start winding down and have to go walk around, empty the dog, remind my wife I'm alive, and see if another chunk is ready to be typed. One of the joys of writing as a hobby is the lack of deadlines
A fair amount of the time, I know a scene or some characters are ready to be written and I sit down with the situation in my head and let the characters just roll, those run about 3-5k average, though they've been known to go till my fingers just can't type anymore (pushing 25k words). Those are always the most enjoyable and interesting for me (both in terms of story and the writing process itself) because I have no foreknowledge of what will happen and I am essentially reading the story as I type, and I've surprised myself more than a few times as the story goes off in a radically unexpected direction before it goes back to where I know it'll link up with something already in store.