But then I will always have a partially worn rear tire, so it will have a diminished lifespan compared to just putting a new tire on the rear. Moving a half worn front to the rear means 3k as a front, and at the absolute best, 1.5k on the rear, meaning it lasted 4.5k miles. Left alone as a front, it's good for 6k. That "new" front will move to the rear with only 1.5k on it, meaning it's only 1/4 worn, and should last... 2k? Maybe 2.2k?

It's a hassle. I average just over 1,000 a month, so rotation seems pointless anyway. Same reason I don't clean chains anymore. They'll be dead within 12 weeks of installation, no sense in fussing over them.