SNM:
It depends on pacing, but in general I feel that anything longer than five or six thousand words should be broken up into two chapters.
Boy, do I agree with that.
For me, I'd rather see a part 1 and part 2 etc... than a 5,000 word story. I try to keep my long stories between 2,000 + to 3,000 +. I may have gone over a few times as SNM says. Many authors on the LSF write really well, but to me seeing a 7,000 word story just kind of makes me believe it's more of a short story with a bit too much sub-plot to it.
I like to see the character(s) identified to begin with. I want to see what they're doing and what they're saying. Then comes the problem. What did they do? Who do they have to report to in order to make amends? I like a little story behind it, but I don't want to read a whole life story about them. A good build up to the actual event isn't bad either.
More than one spanking? Sure. It happens in our stories all the time. It happens in mine quite a bit. I do this because there are times I use F/m F/M and M/f M/F pretty often. This in my opinion gives a little bit to everyone with a preference to orientation.
Details are great. I love to get a comment about how I wrote the details and description of the spanking, both in dialogue and descriptive data. This is what keeps us slavering at the mouth. Where does the spanking occur? Well, we have those who love college type spankings, school spankings involving both female and male heads, maternal and paternal spankings, older sister and brother spankers, housemothers, mother-in-laws, etc... A person can go on and on.
I also like put put a few OW's, I'm Sorry's, Pleeezzzzzzz, I'll be good's, etc... A few CRACK WHACK, SMACK, but not go overboard as the LSF help section says. There are times I describe the spanking without the use of those buzz words. There are other authors who are excellent at it, too.
How is the spanking done? OTK, Over a chair, Over a desk, Over a bed, fully nude, naked from waist down, (includes pants and panties/knickers/shorts down to ankles)? This all has an effect on the reader as well.
Then comes the implement. We all have our likes and dislikes. It's all in the creative writing and the imagination. We get away with a lot in the LSF with our spankings. Are they plausible? Who cares? We just like a good spanking story.