E46 facelift 318i reliability/issues?

Bought a beautiful 2003 model E46 318i (facelift) just over a year ago at a dealer. Full Service History. Probably paid a bit too much at R67k. Car was basically a 2 owner car, both previous owners probably doing long distance driving and really looking after the car. Bought the car with 232k km on odo and just after a service at Continental. Car now has 251k km showing. Due for a Service soon. I did however do the fresh oil (Castrol Edge) and filter thing on about 242k km. This 25k km Service intervals that BMW specifies just don't feel right too me!
Got a printout from Continental, and from that it clear the previous owner did not hesitate to replace rather than repair! Car really going well. No smoking/oil usage at all. The car too feels and drives like new! BMW quality that!!!
Fuel consumption is remarkably good, 7.4L/100km (13.5km/L) @ 140km/h. I even got that figure down to 6.9km/L (14.5km/L) @ 120km/h the other day! Town driving (small town, stop-start) is not so good at 10-11L/100km.
Remarkably good performance too, better than the pre-facelift E46 320i. Friend has one, and my 4 cylinder 2 litre engine definitely has more "go" than the 2 litre 6 cylinder engine with half the km reading mine has. The 2.2 litre engine in the facelift model is apparently a gem.
Getting to my question now! What kinda mileage can these 4 cylinder engines do before an overall? Mine is mostly used for the open road. Got a E12/8 518i as daily runner.