Finger stretches are a good idea. My hands cramp up sometimes too, and I fix small things for a living. Makes me feel like my hands are older than the rest of me.
Have you looked into those hand exercise routines from carpal tunnel guides? I read that people who do detailed work all day should stretch their wrists and fingers regularly to keep things loose. Something about tendons getting inflamed from the same motions over and over. It really does make your hands feel worn out before their time. Maybe adding a few stretches before and after work could help with that stiff feeling.