I imagine, shorter stories are more likely to post quickly
I tend to write short stories of under 10,000 words, novels of 35,000 to 70,000 words, or sagas of 70,000 words and up. The short stories go up in one post, the novels and sagas I tend to post in 5,000 to 10,000 word chunks. That's because I hate it when I see an author has posted a new chapter and then it only takes me a couple of minutes to read and it's taken him a week to do that. That's one of the reasons why I rarely read on-going stories now, a couple of authors did that too often. I figure 5,000 words is the minimal nice read, and 10,000 words is a good read without keeping them up all night. I use the options in SoL to ensure it gets posted with a new part every other day, regardless of what I'm doing. Some of my stories take over a month to post, they're that long, and some are up in a week.
Another advantage my system has is when I start to post the story at SoL I make an e-book version available of the full story. That way anyone who can't be bothered to wait for it to appear at SoL can spend a few bucks at Lulu and get it all at once.
It all comes down to personal choices. I prefer not to post until after completion because it means I can makes changes to early parts if I want to alter the direction. It's a more convenient way to manage the overall story. I have the story appear a part every other day to keep it on the SoL home page longer and get it before more readers, I use the every other day cycle because it keeps the readers' interest and eventually has something being up on every day of the week during the posting cycle. I think this is important because some people check SoL on a specific day each week, and can miss things posted on other days.