Some people like me find cardio very boring when we do one type of exercise. Although my cardio sessions at the gym are around 30 minutes, halfway through I switch between the treadmill, a bike, stair stepper, rowing, etc.
Prime, I do the same. I love walking outdoors with the dog, the wife, the nice weather. Dog moves us at a fast pace, up hills, around the neighborhood, etc.
During a 1-hr walk, I do have a point (1/2 way) where I might sit for 5 mins, mainly for the back issues to ease.
In the gym though, I find myself doing 10-mins on treadmill, 10-mins on bike, 10-mins on concept rower. Mainly for the boredom of each one.
Seems to make it go by a bit easier...