In my experience they're good for about 5 years of racing with those numbers, your spring pressure and lift is VERY close to mine, and i run the 1.6 indy's. I think you'll be fine for a while. I bought 1.6 indys again for ease of install when i broke one on a pass last year, but next time around i'm going to go for t&ds or harland sharps. I'm currently doing some metallography on em to see, but they all break due to fatigue (if you ask around, once one goes, they start to all break successively, and the fracture surface is a typical fatigue fracture), every one i've seen it initiates on the adjuster threads. I could be wrong, but i'm willing to bet they cut tap the threads in instead of roll them, giving a stress concentration and point of failure initiation. If i were you i'd run em for another 150 passes or so then switch to the next level up.