I tend to go out the back and swing an axe at some firewood for a bit, gets the blood pumping in my arms, and tones my muscles at the same time.
Keep fit and be warm next winter, all in the same go!!
I think the main thing is just to not have your hands locked in the same position for hours and hours.
So if Im in at night, and going to be doing things in big batches, Ill have a couple of little bits and pieces I can tick away at for five minutes or so, wander off, have a coffee, work on something else for five or so, at least somethings getting done, then get back into it.