I am way too anal, so I have a spreadsheet on each vehicle with part No, description, category, date of install, mileage, source, costs, totaled to the bottom.
I have more $$ in parts on the wagon than any other vehicle I own. It just took more parts replacements to get it right due to the mileage.
When in doubt replace it......

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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