At my age, there's no pleasure in walking if you have to rush around like something demented, just for it to be aerobic. When DH and i were both working, we used to power walk two circuits of our local park in the early evening. This was not benign exercise as half the park was set in a very steep incline (they used it as a ski slope in the winter!). Whilst it had undoubted health benefits it was not pleasurable! A steady five mile walk, or even half that distance, including a few gradients and stiles, taking in what's around you, is good not only for your physical but also for your mental wellbeing. And as Triciaf says, you meet some lovely people! Mind you, some of the stiles are getting to be a bit of a challenge these days!