^I wish mine were aluminum. Mine is steel. I might look for one of the aluminum ones for some weight savings.

BMW's reason for replacing those bolts will probably never be known. Could be anything from liability avoidance to something more insidious like not wanting DIY'ers to service the transfer case, drive shafts, etc. Generate more money for the dealer service departments after warranty. Or worse, drive more sales of new X5's. Could be anything.

As with most here, I'll keep reusing them until the bolts snap during torquing. Cost of the bolts sucks, but if they were head bolts, they'd be getting replaced. As of yet there has been no demonstrable reason to replace the stiffening plate bolts, regardless of price. Suspension lock nuts are "single use" items as well, but they get reused all the time also. And they are extremely cheap...

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)