@Yuuki Ooooh, I actually went back to check on it --
you're right. JKR said she married Ron+Hermione as wish fulfilment (I thought it was Harry+Ginny that was wish fulfilment) and not because of credibility. She
didn't say that any of it was wrong, or non-credible. Imagine -- they could've actually experienced character development in the intervening 10-20 years.