No, not that! We all know that is an impossible question to answer but it did get your attention.
I mean, how long should erotic stories be? To my mind, erotica has to be short. If a story is too long it becomes romance with erotic elements rather than erotica. I consider that a good thing, after all, erotica is, or should be, so steamy and arousing that after any more than 4000 words you will be aroused to the point where you can't concentrate on reading and need a break. That's certainly how I try to write and it's why I have no intention of writing anything longer than a short story in the erotic genre.
I love the excitement and the roller-coaster like pace of flash fiction or short stories and perhaps more importantly, the immediacy of it. As a writer it is probably lazy of me because I don't need to create a decent lead in or create any kind of consequences. I don't even need to worry about character development or justify any of the character's actions. You could say it's the perfect one night stand of the story world, a snapshot into the lives of the protagonists rather than a fully developed story and really that's all I'm trying to create.
One aspect I do take time over is the physical attributes of the characters in my stories. I think it is very important that authors should not copy the mistake of our mass media culture by espousing perfect figures. How many times have you read a book that featured the perfectly toned billionaire male being won over by a coquettish young woman who is slim, pert and perfect? Is that you? Then you're lucky. For the most part, readers (i.e. us) are not the perfect physical specimens portrayed in movies and magazines nor should we aspire to be. It is very important that we learn to be happy in our own skin and not to judge either our happiness or that of anyone else by their physical appearance alone. As a writer it is definitely possible to avoid the age old cliches and to allow our creations to be 'normal'.
I'll hold my hands up here and say that it's very easy for me to be righteous about this. After all I only write short stories and I don't have to worry about fleshing out my characters. Of course in reality writers never have to flesh out their bodies, that should only ever happen in the reader's mind. Writers lead the imagination and provide triggers for the reader but don't need to provide complete descriptions in infinite detail. Don't believe me? read Stephen King's book "On Writing". He really does know a few things about creating fiction and has some superb examples in it.
Next time you read something, think about the physical attributes that the writer has used. Are they pushing a perfect physical specimen or are they leaving it to your imagination? It's up to you as a reader to decide if you are happy to be spoon fed the same old stereotypes or to seek out writers who let you use your imagination and create characters closer to you and me. The choice is yours, vote with your eyes and your fingers but I know which way I'm going to go.