So, this weekend I installed the new PR5 I mentioned earlier. With experience I'm gaining in installing so many Wee tires, I think I'm getting quite a lot better at it. Other than it being really hot and humid outside, things went quite well.
While I had the tire off, I balanced only the wheel. When I then installed the new PR5, it took only two (1/8-ounce?) weights to balance it. I remembered, this time, to equally distribute the weights on both sides of the wheel.
I changed it at 43,850 miles (wanted to push it to 44K miles, even, but the cords were starting to show). Anyway, that's 6,850 miles on the PR4 that was on it. Pretty good for me. Will plan next rear change for 50K miles, and probably check the engine valves, again, then, while the rear wheel's off the bike. (This assumes I haven't traded bikes, by then).
Bike's running great though. Riding it to and from work is often the highlight of my day.