I ordered mine just before new years and was told it would take about 5 months for my Hayley Paige/JLM Couture dress to come in. It took two months. I was annoyed because I didn't get to save for 5 months as planned to pay for the rest of the dress.
6 months the first time but they ordered the wrong size so it was a total of 9 months before I got one that fit correctly. They had to rush order the replacement.
I was told it could take 6-8 months and it arrived at the boutique 3 weeks later. It depends on the designer and how busy they are at that specific time