I've had 3 X5s, 2 e53s and 1 e70, will be going into my 4th e70 in the next month.

I've always gotten the sport package and the largest rims available for them at the inception of each lease. My driving habits are aggressive at times, and on the first X5 I wore down the inner edges of the tires much faster than I expected. I think I got 13k miles on performance summer tires. At the first tire change the SA who I befriended advised that I get an alignment to switch the camber and toe on the e53 to the lowest spec value that BMW recommended. If you are familiar with BMW camber and toe, you know that they vary anywhere from -1.5-2.5. After the changes I got to 6k on the same second set of tires before lease end (20k mile lease term). The next e53, I had the same (brand new set) summer performance tires with alignment done, I went the full term of 20k miles with maybe another 3-4k left in them. On the e70 I switched to all-season tires from OEM and they lasted almost the full term of the 36k mile lease with more thread to spare.

Before taking delivery of my next 2011 e70 (20" style 336 with OEM RFTs), I'm switching out to all-season Conti DWS non-RFTs from the current OEM RFTs. I will also be getting an alignment to do the same thing. I'll switch back the the OEM RFT at lease end. The Contis should last me almost all the way to the end of the lease (45k mile lease this time).