We can't take off the end of August and most of September usually, because our annual convention in October, too much last minute stuff to get ready for the conferance. Starting about 2 weeks before the convention, it's okay again, because in my department, most of the work is done even though the convention hasn't started yet.
In fact I picked my wedding date due to my convention last fall, I wanted to wait until after it was over so I was 100% sure I'd get the days off for the honeymoon!