Congratulations, that is amazing! I personally do not know how you put on 250,000 miles on it, mine has 112,000 but what problems have you encountered on this car? I just got mine from my uncle and he took great care of what he knew how to fix but unfortunately that knowledge had nothing to do with the engine so I had a few minor fixes like transmission seals, gasket, and a/c compressor. Back to your question, of course you should go for 500,000km because its too much work to sell it.