You have 17's, so you'll have a better chance of not getting bubbles from potholes before end of life. Problem is life expectency is still short when compared to regular tires. I would guess maybe 20,000 if you drive combination city/highway. More if most of your driving is highway, less if city. My suggestion would be to make sure you've setup a tire fund just in case.
I have a 528i with 14,600 miles on it so far. It came with Eagle LS/2 ROF and the front tires have 8/32 tread depth, the rears have 7/32. I don't know what they started out as, so I can't tell you how much more life they have. I tend to drive fairly gently most of the time with an occasional sporty run every once in a while. So far, I have been happy with these tires as they seem to grip the road fairly well on turns and are not loud or too harsh a ride. Of course, the ride should be smoother than the 18 or 19 inch tires since they have more sidewall height.
The RFT's on my '08 335i were at 42K miles when I sold it, and still had about 5/32" tread -- probably translates to 10K more miles. I had non-staggered M+S 17" and I rotated them at 8000 mile intervals when having the oil changes performed. I expect the 18" RFT's on my F10 535i to wear comparably.
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