I’m glad I posted this question. I’ve been given much ‘food for thought.’
Here’s a quick analysis. If you rotate tires every 6000 mile on average at $20/rotation that comes to $140 or $35 per tire. If you are buying ‘ordinary street tires’ you can probably get them for around $150/tire. This suggests that you need to realize over a 20% increase in average road life on the 4 tire set on a car (35/150 = 23.3%.)
Is this a realistic expectation?
The Leaf in question is driven 4500 - 5000 miles/year and represents >90% of the miles we drive. We are both retired, so there is no daily commute involved. I’ve not done an exhaustive analysis, but my guess is that >60% of our driving is short trips on city streets shopping and running errands. This inevitably involves a lot of turns, but since the trips are round trips the turns should approximate 50% left and 50% right turns. Some destinations allow some freeway driving at speed. My greatest tire wear concern is sun damage and oxidation. Our cars are not garaged; the garage is storage and work-space.
I make an effort to check tire pressures regularly and to adjust the cold pressure on the OEM Goodyear Ecopia tires at 42 psi to avoid wearing the edges vs the center tread. I learned this the hard way on a 2004 Prius.
The shop that checked the alignment, a large local Shell station, has a good reputation for its repair work. It was recommended to me by another local mechanic with great reviews (Mechanics Files at Car Talk) because he does not do alignment work.
Thanks to all who have participated in this thread. If someone has more to add, please do so. Even at 76 I am eager to learn.