As everyone else has said, banjos can and will last if you drive them easy and don't shockload them. I think running small tyres certainly helps prolong their life too, but that's boring and then you just get wheelspin if you try to launch the car hard.
So it all just depends what you want to do with the car. If you plan to enter performance events and really do some fun spirited driving, be on standby to replace it!
My complete 9" assembly with centre, axles, and brakes for $750 out of the trading post many years ago, was literally the single best thing I have EVER bought for my car
