Monique Lhullier Vneck/Vback with a loose trumpet flare dress available at Nordstrom:
I fell in love with this dress the moment I put it on - it fits like a glove in the bust, waist, and through the thights and gradually trumpets out at just the right place (unlike some mermaid dresses that look great when you're standing up straight, but good luck sitting down!)
Our wedding/reception was about 6 hours in total, and I changed right after (total time spent in dress was roughly 8 hrs).
It has been professionally cleaned as of 8/31/2017.