What's the right balance between active and sedentary time?

Look to be active. Do you exercise at all? If given the choice, do you take the stairs or an elevator/escalator? Do you park close to a building or far away? Do you own a push or riding lawn mower? Or do you have a landscaping service and watch them cut your lawn from the window? Always look for simple ways to increase your activity every day.
Personal. Every person is different and depends on your goals. I would say if you have a desk job workout at least 4!times a week for an hour ronan hour and a half of moderate intensity activity combined with some muscle building weights.