WHEN THEY'RE ON CLEARANCE @ joann's! LOL!!!sometimes people are able to accomplish MORE- one block at a time.

I've never been involved in a BOM group. I'd think one benefit would be the opportunity to try a variety of blocks that you might not otherwise attempt - kind of a teaching thing.
I can see a drawback for me: I complete 3 or 4 blocks and when the 5th block arrives that I don't particularly like or perhaps seems too difficult for me I forget the whole project. LOL