So having taken three cars past the 200,000 mile mark:
1989 E30 325i - 256,000 - 18 years
1989 Acura Integra - 230,000 - 8 years
2006 E90 325i - currently at 200,000 - 6.5 years
My observation is at some time you reach a point where you just want a new car. I do all my own maintenance and repairs and have a decent shop set up to do so. I could keep a car running forever if I wanted to (assuming parts are available), but I found, even with the great E30, new cars offer so much more in refinement and performance, that it is just not worth keeping an old high-mileage car as a daily driver.
My 2 cents.