I need to know if my chapters are long enough

With writing in general, I am often unsure if whether a chapter or a scene is long enough, or if it needs to be trimmed down because it is too long. I'm currently working on a little story based off a hentai game, and I felt that the sex in the third chapter was short, even though given the scene, it was meant to be a quick fix anyway.

Here's the story: http://www.bdsmlibrary.com/stories/c...hapterid=26291 If anyone has any comments or suggestions, either drop them in this thread, or as a story comment.

Thank you.