I have a 2007 E60 N62 550i with 191,000 miles on it. I've been staving off the inevitable valve stem seals replacement with Liqui Moly Oil Saver for some time. My son uses it for his 80 mile daily commute. Didn't pass its CA emissions test due to failing the "smoke check" which is I think just a visual. It does smoke after idling a bit. The oil saver had that covered until my rude awakening today. It's a 14 year old car, it has 191,000 miles on it, runs strong, looks good. Never in a collision. But it does have rough cold start idle related to a worn eccentric shaft (or two.) My son has gotten used to keeping it at a fast idle until it is warmed up.
I'm pondering my options.

Dump it as a mechanics special and buy a lower mileage N52 powered car for him to rack the miles up on.
There are some pro's here, better mileage, fewer issues, fewer leaks than the N62
Rent the stem seal tool and buy the seals and VC gaskets and coach my kid through that ugly chore.
The main pro is that this car is loaded, Logic 7 sound, Sport package (suspension/interior upgrades) heated seats, tinted windows

The main con for the stem seal torture is that the car will still have the eccentric shaft issue and 191,000 miles on it.