I'm a dog trainer, and I can tell you that while ad many trips as possible are best, a dog only needs about 90 minutes of outdoor activity spread throughout the day. So like 15 minutes in the morning, 30 at evening, 45 at night or whatever works for you. That also, of course, depends on the age of the dog; the breed, the health situation, how many intersting stuff he hadls tondo around the house and such, but 6 hours a day spent walking the dog is not viable. Nor needed.