Depending on your overall health, medical condition and need for exercise
, even as much as 10 minutes of any kind of exercise 3-7 times a week can make a difference in your health.
Certainly the more fit one is, the more exercise can be done. I would recommend 30-45 minutes 3-4 times a week and more if can, to keep you at your best health. Speak with your pcp, personal trainer or qualified prof.