15 minutes would be way too short for me. mandy and I usually go for 45mins to an hour, with foreplay accounting for about half that time.
The first 10 mins of actual sex is when I'm at my most sensitive, with sensitivity dropping off slightly after that. That's when it's most enjoyable for both of us, because I can enjoy myself without having to worry about cumming too soon. 4-5 positions later and she'll do something to send me over the edge.
