I am running the Nitto 555 and have 45,000 miles on the fronts --- will change for the 2019 season and over 25,000 miles on the rear. I don't baby them but not aggressive all the time...
Comparing the UTQG among the different rear tires I've tried, I got around 10-11,000 miles out of the original factory rear tire and the Kenda I replaced it with. I then tried a Sumitomo HTR Z III tire and only got around 7000 miles on it. The Kendas and the Sumitomo are both UTQG rated at 300. I then tried a Nankang NS-20 rated at 360 and got almost 10,000 miles on it. The Nitto 555 G2 carries a UTQG rating of 320, so it is similar to the other 3 brands I've tried. I've got a little over 7,000 miles on it now and from the amount of tread left, I'm hoping to get at least 11,000 miles out of it. When I was on two wheels, I typically got around 3 x the life from my front tire compared to the rear and so far I've done a little closer to 4 x that on my Slingshot, but I can't imagine getting 25,000 miles from a rear tire, especially since I am now turbo'd.