I NEVER use an impact wrench to remove/install the covered lug nuts. Do it by hand and they will last forever. I change over to off-road tires about 10-12 times per year (Yes, I know it's crazy, but my 2004 Disco is also my daily driver).
BTW, thanks for clarifying that they are 27mm. I have both sockets, but was never sure which was correct. Nice to know that those 2 sizes are sooooooo close, though.