We have a 1 year old medium sized mutt with strong working roots (maybe spaniel / hound / terrier). She really looks the sort of dog that needs huge amounts of exercise, but to be honest she seems much happier and more settled on the days when she doesn't get much. Her recall is work in progress so we can only let her off in very specific places: when we go for a long walk where she can be let off she have a great time but for the rest of the day is unsettled and barky - I usually have to put her in her crate and shut the door to encourage her to settle and have a nap, but even after she's slept she is really restless. On days when I feel she doesn't have enough exercise (at the minimum we could be talking 1-2 miles lead walk with limitless opportunity to mooch around our reasonable garden plus a bit of training) she actually seems much happier and more settled. If she's happy is it OK to let her have some "chilled" days like that - to me if doesn't feel anything like enough? She's very slim and fit as the architypal "butchers dog".