You do not need to do chain guides preemptively. They can last 300-400,000 miles. My research concluded that the primary failure mode is the chain tensioner . The guides are probably brittle by the time they are five years old or 60,000 miles. The chain is held off the guide by flowing oil like a journal bearing. On the engines I've changed guides there was virtually no wear @ 160,000 mi. The guides shattered when the chain gets loose and slaps against the brittle guides. Either from low oil pressure or worn chain tensioner. If you look at the design of the one chain solution on the M62 you'll see there is a incredible length of chain at the bottom that is subject to whip when the chain is not super tight.

Last year ones of the m62s I help with developed start up rattle, we checked for broken bits of guide and found none, we installed a new OEM tensioner and instantly fixed the start up rattle. Considering that some of these engines have made it 400,000 on original chain guides it's not a given they need to be replaced. That said 160-180,000 might be an ok time to consider replacing but it's more important to replace the tensioner at least by 120,000 then every 60-80,000 after that. One big pothole with a weak tensioner and 3# of chain slaps info that brittle chain guide and it's toast.

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2011 E70 • N55 (me)
2012 E70 • N63 (wife)