In my opinion don't spend the money, my reasoning:
I have a 36 month lease.......
Pirelli's come with a manufactures 1 Year full road hazard replacement, then something like 60 % for the second year and 40% for the 3rd year
I have had to replace 1 rim in the last 15 years of driving (pot hole)
BMW does not cover cosmetic damage
Had a flat (nail) after 6 weeks, total cost for new tire was $65 for install, so I figure I'm still $1400 ahead in my pocket
lastly, I rather spend $800 for a brand new set of tires 24 months into the lease so that I know that I'm driving on good tires through the entire 36 months, instead of worrying if I drive on the originals for the full 36 months will the dealer say they are not within the return guidelines and want to charge me $1800 at the lease termination