If the engine is built properly,and treated properly,there is no reason why it shouldn't last.....prior to my S3,I had 2 Cosworths running not far short of that power,and both were reliable,and fast.
That said,the A3 2.0T is not such a good platform to start with as the S3,and it would need a LOT of work to get anywhere near 500bhp.....there are a reasonable number of 500bhp S3s running around.