Meditation duration
If each day you can meditate for an hour, it would be excellent! If you can do it only half an hour, it is still helpful. You can split your meditation. Half an hour in the morning plus another half an hour in the evening gives you an hour of meditation for that day.
Any minute you meditate counts. Just closing your eyes for 1 minute or 5 minutes offers a good break in any busy situation. It will be good to create a habit of bringing your mind to rest at the center. The more you can bring your mind to its right place at the center of your body, the more healthy and well maintained it will be.