I'm in TX also. Recently replaced the Dunlop runflats with the Michelin Latitude all-seasons. The all-season tread is not as aggressive looking, but they ride much better than the runflats and I haven't noticed any drop in handling capability.

My Dunlops had about 6K miles when I replaced them. My guess is I'd be lucky to get a total of 12K miles out of them. The new Michelins should last much longer (and they cost a little less).

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2008 X5 4.8i, Jet Black, Tobacco Nevada leather & just about everything else (no vent. seats, no 3rd row)