I replaced my tires with a new set of PR3s today. The front tire was a PR3 that that 17,125 miles on it. It still had tread, but not much. The rear was a Dunlop Roadsmart 2 that had 8950 miles. It had replaced a PR3 that I'd found a nail in the morning of the day I left to try a Bun Burner Gold on the way to the National Rally in Spearfish last summer. I didn't get the BBG, but the Stop & Go plug I used lasted for 1500 miles. The morning after I got to Spearfish, Rick and I and somebody else (was it you, Tim?) went looking for a PR3 for Rick. We couldn't find one, so instead we got breakfast and when we came out my rear tire was flat. There was no sign that a plug had ever been in the hole and we couldn't get one to stay in the tire. We got some gummy worms from K-Mart and they worked to get me back to the campground, but wouldn't completely seal the leak.
I ended up finding the only 150/70x17 in South Dakota (well, maybe not, but the only one I could find) at the Honda dealer in Rapid City.
The Roadsmart 2 was OK, but it was really squared off. I had planned on riding it to Texas at the beginning of May and then replacing it with the PR3 before we headed out on the Epic Road in July.
I'm pretty confident that you'll get close to 15,000 out of the rear PR3.
It's the only tire in my experience that will get you that kind of mileage on an NT.
When I had the Concours C-10, I ran Goldwing 1500-sized bias-belted tires. The Dunlop Elite K491, the Metzler 880, and the Michelin Pilot GT all gave me 15-18,000 miles on the back and 20-24,000 on the front. But they didn't have anywhere near the grip that the PR3 did.