It sounds like I have big end knock so will need a re-build of some sort. (2006 WRX, 54,000 miles). There are lots of posts about forged pistons, hardened cranks and the like, but is there any evidence that a 'stonger' re-build engine actually last longer than the original?

Please, if you have had your failed engine rebuilt, how many miles has it done, and how many miles had the original done?

 

It all depends on how you treat it/ tune it/ look after it. A poorly looked after or tuned forged engin wont last too long regardless.

 

It should last the same as the original, ie ideally well over 100k miles, if not a lot longer if forged. As above, as long as it's looked after, always driven very lightly for first 10-15 mins to warm it up (same as normal engine) and always serviced, and if tuned, done properly and safely with a reputable tuner, it should last years.