Yeah, parents will do that. But, ultimately, if you explain the benefits and how necessary the move might end up being to help you to be where you need to be in life, then I don't see how they could condemn you. I suppose it's a little practice in persuasion.
My parents and I didn't really have the discussion until after I was offered a place. I had to make clear that I wasn't "running away", that I planned to go back to Melbourne every single break, I pointed out how long the summer holidays are (3 months or something), etc.
My dad still guilt trips me, I think. I don't think he completely understands the way I think about education. He seemed to want me to go to uni to become a journalist or go into marketing or something that he sees as well-paid/useful (now he seems set on my getting a government job of some variety). But my mum doesn't seem to mind as much as I thought she would. Actually, last time I was in Melbourne she said that she supposed that it was probably good for me to get a chance to move interstate, because she's lived in the same region of Victoria for most of her life. Nor has she ever lived alone (not that I call college life 'alone'). So yeah, if you do end up going, they'll get used to it, they may call you just about everyday though. They object because they love you, but the onus if on you to show them that applying interstate is in your best interests.