The Kinetics of Rut Formation

The other day, as I was taking the back roads up to Durham, I was deep in my head and not noticing the intense verdant scenery rolling by. A curve, then two, rolling hills, a rye field bordered with bachelor buttons, then a tunnel of shade through oak forest, and it was a while before I realized how beautiful everything looks. How long had I been driving blind?
I had a networking lunch last week with a person I met through a friend from choir here. As we went off to our blind date, she asked me where I wanted to go, and I listed off the places we've gotten used to, and soon saw that for as little as we've been here, with all the restaurants we have yet to try, we're already in a rut of old favorites.
How long do ruts take to form? I have a running fascination with pioneers, those folks who packed off their best stuff into covered wagons and went West into terra incognita full of confidence that everything would go well. I often feel like something of a lily-livered whiner for how easy my life is compared to these hardy folks. I remember reading that their ruts across the prairie are still visible more than a century later.
Ruts are powerful things, powerful imagery too. My great grandfather who was a carpenter was also a cartwright. I only have one photo of him, a huge man (built as an armoire as we say in French) and you'd have to be, because making a wagon wheel means you use a tough tree knot for a hub, and he would have used a hand-cranked drill press to drill through it. I think of those big wood cart wheels stuck in ruts, if your horses or oxen shied, the ruts could tear your wheels apart, so turning was hard. Is hard.