"Impromptu" or same-day sessions were the only thing when I started back in the 1970s, even later, after I took a break for several years and returned in the 1980s, especially when you consider the many dungeons that Manhattan used to have, with several dominas to choose from.

I can see both sides of the discussion, but in my experience impromptu sessions can be edgy and a lot of fun if it is with a Mistress you know pretty well. To do one with a Domina you've never met, or met just once, would be more difficult.