I thought they recommended service at one year regardless of mileage if for nothing but to rotate tires and check fluids.
Which reminds me. I gave BMW a lot of consideration the last time I bought a car. I just could not get past the insistence on run flat tires. It's a characteristic of BMW anyone considering one of these cars should understand before purchase.
I'm not sure on the X5, but on most BMWs they recommend not rotating the tires. There are two reasons. One is that the rear suspensions have negative camber so if you brought the tires forward there wouldn't be as much cornering grip as the edges of the tire would have a bit of wear. The second is that since BMW designs their cars to have 50/50 weight balance, there is equal weight on all tires so the tread should wear more evenly than tread on other vehicles.