[rocco33]

My working labs (high drive) get a couple of 30 minute walks, one in the morning and one in the late pm/evening. Other than that they veg out on the sofa. They CAN keep going all day, but one of the traits of labs (at least working ones) is that they have an excellent on/off switch - it's essential for a working lab because of the job they do.

I agree with Swarthy - a lot of exercise will wear them out for a while, but really, all l you are doing is increasing their fitness so they require more exercise. Mental stimulation and exercise is much more tiring and results in a happy contented dog.