Well, in my opinion once or twice a year does NOT ruin the magic!!
But, last year we went 5 times throughout the year, when we normally just go once in December. Well, by the time December came around I wasn't as excited to go as any other year. It didn't ruin the magic, it just wasn't as exciting for me.
So, after last Dec. we decided that for 2008 we would restrain ourselves, and hold off until this December. A hard feat, let me tell you! I am SOOOO excited, I can hardly wait- 46 days to go!!
So, my theory is that like in all things in life, if you have too much of it, it can stop being as "special".