I'm going to take a stab at this and say that the length/detail of any sex scene is serviced by its purpose in the story. If your story doesn't need ten pages of heavy breathing and button ripping, cool. Don't get yourself into a tizzy about writing it.
I have two completed novels under my belt, each one very different from the other. The first was written several years ago and there is one scene near the middle-end where two adult characters have sex in a hayloft. The purpose of the scene is to show that these characters have found a common need for each other. There is some kissing, some verbal prompts, and then a nice little "fade to black" moment. The rest of it is left to the imagination.
The second novel gave me more trouble. The sex scene that the story demanded was a desperate coupling, where one person needed the physical comfort/connection to try and ease a painful loss.
I was scared as anything to write this scene, and found great advice on a different sort of message board. Read online erotica. There are all sorts of sites out there that aren't porn, persay, but still host erotic stories of all detail levels. It was good advice.
I'm not saying that this tactic is for everyone, but it helped me figure out how to write my scene. The choreography, the euphemisms, ect... It felt no different than researching the pineal gland. The story demanded both things (sex and the pineal gland, although not necessarily in the same scene

), so I researched them.