Sitting for too long and staring at a screen can be bad for your health.
Sitting to long and not moving around can cause loss of proper blood circulation and can lead to blood clots. You should could get up and take frequent breaks from the computer.
Get up and walk around at least every 30 minutes.
Staring at a computer screen too much can also cause eyestrain and headaches.
Sometimes people do have to stay on the computer for 10 hours a day though because of their job to earn a living.