Toe outside of specs will wear tires much faster than too much negative camber but the greater the negative camber combined with a conservative driver the more negative camber will contribute to tire wear as well.

I think using the minimum spec but within the range of specs that will contribute to less tire wear is very reasonable. Settings out of spec are going to negatively impact driving and handling characteristics. Potential downsides you may dislike more than improved tire wear with an out of spec alignment are things like darting around the lane, more difficult to drive in the rain or less predictable around a corner.

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X5 4.6 2002 Black Sap, Black interior. 2013 X5M Melbourne Red, Bamboo interior
Dallas