Having driven BMW and other manufacturers well past the 200K mark, I would say what others have posted. Get a base line of where your vehicle is at today, any good Indy BMW shop can assist. Suspension, drive-train, electronics, cooling system, Brakes, etc. Line up the results that need attention in two buckets- Safety-performance (need now), keep you eyes on it (Long Term).

Plan on repairing/replacing everything in the short term column, add up the prices of repairs, make a decision - Keep or dump. Real simple.
The more you can handle on a DIY bases will allow you to stay longer, save your wallet from impacts, and make you a happier owner. The more other do for you ($$) the greater your pain will be. Wrenching on cars is like working on your home/house. There will always be projects needing attention/ completing. The more completed the less there is to do. Think of it as therapy for job related stress.

The forum is here to help on these 10+ year old cars. With age, costs go up. That goes for humans too as 80% of your medical expenses will occur in the last 20% of your life. When do you want to pull the plug on Granny? How about yourself?

When I worked at a Dealership the rule of thumb was less than 4-6 car payments? Fix it. More? Trade it in on a new one.....

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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