damn....the thread got this long already?
Anyways, i don't know what advice to tell you except:
Having a drag-out, long sex isn't always good. Sometimes, quickies are a lot more pleasurable.
Key point is to keep the partner please and reach her climate as much as possible. If you can make your partner come 3-5 times within 10 min, that's good enough already.
It's also about intimacy and romance. Trying new things together, will definitely a turn on.
Believe it or not, many of the ladies said that they do not want long sex. It's when they become dry and it's not pleasurable. 20 mins is where they want, as long as they feel the pleasure.
Like John said, foreplay is very important and one of the most enjoyable part. The key is to know when to take the action and when to stop.