I/we try to get ours out at least 2x day now that I'm back to work full time.
I used to take them out 4-6 times a day when I was home. If I or hubby get home at lunch time we take them out for the 3rd time of the day. We probably walk a total of 1 - 1 1/2 miles a day depending if we go 2 or 3 times a day.
The vet told us it was good for them. We don't have a fenced in yard for them to run around. I do keep the door to the sunroom open during the day but it's just not the same as a yard.