actually they are only prone to failure if you don't change the belt to schedule - then WHEN it does fail things get messy (note the b230f is - theoretically - a non interference engine so you can 'get away with' a belt issue, the b234 most definately 'interferes')

I never understand why people have issues then complain, its simple you change timing belts to schedule (unless your like me and figure that twice as often is a good idea...) OK you CAN get mega unlucky and have one fail early - but lets face it you could get mega unlucky and have a con rod fail for no apparent reason but it aint likely! - if you dont change belts sooner ort later they go and when they do its your own fault....

Timing chains are worse to change/adjust/service and if you have every seen the mess when one snaps (I have - admittedly my guess is it was doing about 20k rpm when it let go...) you would think a belt was a fine idea!

My experience with many cars of 100's of thousands of miles is providing you change them you dont get issue - and its the first job i ALWAYS have done on any car I buy REGARDLESS of what the history says....

think of it as cheap insurance...