At first I ran everywhere, but now I walk when I'm in high RP mode (as opposed to "do the quest" mode). I usually do it in 3rd-person, to make sure I keep it to a walk or slow jog. The longest I did was from the far northwest corner of Falkreath Hold back to Falkreath. My character was mad at Faendal and did the whole thing in silence. There were no encounters, and I kept it to a walk the whole way. But I usually jog, alternating it with walking. I'm not completely mental.

I just figure my character is young and in shape and can jog for a few miles at a time, as I could when I was younger.
I'm currently walk/jogging through Eastmarch and the Rift, trying not to do the main College quest line and resist other tempations to fast travel. I've learned not to get completely loaded down with loot when out in the middle of nowhere -- the temptation to pop back to Windhelm to sell it proved irresistable. But then I FT'ed back to where I was and resumed walking. I'm determined to walk to Riften.
One reason I do this is to drag the game out as long as possible. I'm not in any hurry to finish anything.