2010 535i GT - question on add on warranty

hi all,
I picked up a CPO 2010 535i GT last week and i've been greatly enjoying the new ride!

ive been reading the pros/cons of the runflats and the pros/cons of the additional warranties offered by BMW around the forum but generally i take from this that a good portion of the need is really regional.

I was wondering what experience folks can share with the 18 inch tires. Ideally any of the greater denver, or other areas at altitude would comment on their experiences with these.
i have the 18" Goodyear tires.
as to the glass. they are offering a program for ~650 that gives up to 2 OEM windshields a year. i know we sand everywhere around here so again, wondering about peoples experience.

many thanks!