I just ordered one and I was told that 3-4 months is usually how long they take, but a larger or smaller BP can take longer or shorter, and it depends on if you''re ordering in peak season or not. Since I just ordered a single dress, I''ll probably get it closer to 3 months than 4. It''s also a good idea to give BMs at least a month or even a touch longer to get alterations/hemming done. The dress in the size I just ordered will *likely* be too big in the chest and hips due to the size I had to order, which is pretty normal in terms of how BM dresses are sized. Very few people actually fit the measurements of the stock size.
I think maybe 6 months or so if you go with a typical bridesmaid dress brand.
But my wedding is in July and my bridesmaids are wearing J. Crew dresses, so they just ordered them when J. Crew had a 20% off coupon code. 2 already came and 1 is on back order until April. So I don''t think it''s a huge deal if you do it closer to the wedding as long as you like J. Crew BM or other off the rack dresses.