For the money I would shy away from the G614. When you can get a Hi-Spec Alu wheel and Cooper Road Master for $460. Rated at 4805lbs and a much stronger sidewall then the G614. These tires have a much longer road life as they are still good after 6 or 7 years before needing replacement. This is the option I would consider on a Tandem Axle TH. Triple axle you could proably get away with the G614 and be fine.
I just got the price a few minutes ago, Shipped to me in houston on those was like $1950. http://www.trailertiresandwheels.com/site/1284278/page/910782 They dont have the tire listed on the website. Now I just have to convince the wife we need these
I did the roadmaster tires and 17.5" wheels myself. So far so good. It was amazing how heavy truck tires are.
Best thing you can do for any tires is balance, full air pressure and don't let them dry out.
Doug