My '03 has been an absolute maintenance hog since passing 90k miles. I bought it in '06 with 43k miles and have had pretty much every failure that is documented on XO. Now at 145k it is well sorted and I have not had anything happen since the beginning of 2022 but the intervening 50k miles have taught me more about the e53 than I ever wanted to know. However, it is a great car to own and I am not considering parting with it.

My kids pretty much use this as a DD to their respective colleges and it serves as the grovery-getter since it is the smallest vehicle we own and hence easy to park.

Is it worth it? Only if you have: a. another backup car, b. ample time on your hands to wrench, c. know how to use the BMW software on a PC and d. you can spare the 3k a year (on average even with DIY) to keep it running. It is a hobby object more than a car.... :-)

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2003 4.4i black ext./black int./black headliner (kid's runabout)
2014 535d X-drive, M package, silver/black interior

Sold but not forgotten:
2009 E70 35d, black ext./black int./black headliner (sold 2021)
2006 4.8iS Le Mans blue/cream int./black headliner, SOLD in 2012 sadly...

Other hardware:
2015 Cayenne S (wife's new DD and definitely wroooommmmm)
2016 Tundra 1794 edition crew cab, luxo hauler
2005 Tundra crew cab, weekend hauler. Sold after 150k very happy miles.