I would say it depends on the moment and the situation. Also I do not think it matters how long what it really matters is the quality. Sometimes it may just be 15 minutes other times it can be an hour or even more. It also depends which games you play and what you consider sex. If for you sex is just penetration or also the playing game before penetration.
In a session? Until we're both done if I'm not tired we would have some foreplay beforehand and might take 20-30 mins or so, but usually I'm too knackered for that so it's more of a quickie 5 -10 minute job.
Ok, say from initial instigation, so that would include foreplay. I completely agree that it's about quality. I think it's the time and energy that we just don't have. Kids around, shattered after bedtime. One of us falls asleep on the couch, but I was assuming that was normal. Even if we had hours to spare, I don't think we would have sex for hours. Maybe we have just gotten used to doing it quickly!