Short version: After 2.4 yrs of leasing and 55,000 miles, I'm thinking
of keeping this car.

 Long version: My car is my mobile office.  I do about 70% local
roads, 30% highway driving.  AWD, handling, braking and acceleration
are excellent.

 I'm thinking of buying the car at the end of the lease, because of
the mileage overage penalties, and damage penalties - those two
combined will make a turn-in very painful.

 So... for the long haul, how do I keep this car running well at reasonable cost?

 Historically, what tends to go wrong, and is there anything I can do
to forestall or prevent these issues?

 
I can't avoid the heavy driving, since I make my living out of my car.