No hard stats on vehicles still titled vs parts sold. Would make an interesting grad student marketing project.....
It only seems that way as most everyone has had a failure sometimes in the E39/E53 life. The funny ones are the ones that fail on in garage queens that are just sitting there on battery tenders. I haven't been bit yet but my personal thoughts are I am on borrowed time as three of my cars just sit on tenders.
Indication of super high replace cycles.
The part is now available as a Chinese knockoff, the dealers near me stock 5 at a time due to high demand on 10+ year old cars, and every shop that tinkers on BMWs locally are experts as they are seeing a few each month around here.
All antidotal elements though. No hard stats just frequency of hits on the DIY articles.

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2005 X5 4.8IS
The Blue ones are always FASTER....

Current Garage:
2005 X5 4.8is
2002 M5 TiSilver
2003 525iT
1998 528i
Former Garage Stable Highlights
2004 325XiT Sport
1973 De Tomaso Pantera, L Model
1970 Dodge Challenger T/A 4 sp Alpine White
1970 Dodge Challenger T/A 4 sp GoManGo Green
1971 Dart Sport, “Dart Light” package
1969 Road Runner 383
1968 Ply Barracuda 340S FB Sea-foam Green