My friend and I make our own retreat. My DH and DD go to a basketball tournament in Las Vegas, my friend and I go to sew/quilt. We have 4 full days of sewing. We arrive on Tuesday afternoon and leave on Sunday morning. Since we have 2 one bedroom condos, one is for my friend and our sewing. We get up and start sewing about 9 am and sew until we want to break for lunch. Then we go somewhere for lunch, find a local quilt shop and return and sew until we decide it is dinner time. We have snacks available, we do what we want and stop when we are too tired to sew anymore. We leave our sewing out and come back to it at will.
No one criticizes our mess - so far we have used it to finish projects. But one trip we cut out a DWR quilt using my GO and she brought her embroidery machine to make some quilt blocks.
I haven't gone to any formal overnight retreats mainly because they want you to share hotel rooms, and I really don't want to do that.