Congratulations! I too had a long engagement (6 years, due to college 120 miles from himself, and subsequent lack of money). I wish them both every happiness.
My son moved out 2 years ago to live 230 miles away down in South Wales, and #1 daughter has just moved out a week ago to live with her long-term boyfriend. I was dreading the old empty nest bit, but she has so much stuff that even a week after the move, it looks like she's still living here. She has only moved about 4 miles away, so it's a gradual emptying.
#2 daughter will be off to university in a year's time and then I will really feel the empty nest.