Not to worry. That's quite normal, even if it happens with you every time--if, of course, your equipment always functions properly up to that point. It's an individual thing--sometimes shorter, sometimes longer, as Nubstar notes, and different for different men. Can depend on various outside factors, too: whether you're rested or tired, rushed or leisurely, time of day, location, etc. And it makes a world of difference whether your ejaculation is from masturbation or partnered sex. As a gay man, I can't begin to recall how many post-ejaculation subsidings I've seen, and tihe timing is always completely unpredictable. Some immediately, some "intermediately," and some "pesistentmediately". If I'm with an exciting partner and really turned on, I often literally don't subside at all until after another round or until we conclude the session. Many times I've received this reaction: "You're still hard! Don't you ever go down...?!" With masturbation, lacking the excitement of a partner, my interval varies, but most often is quite brief. (I've wondered, by the way, why Viagra warns about a 4-hour-plus boner--but I suppose a chemically induced erection is much different from a lasting natural one, since without chemicals the body can choose its own "deflation" time.) -- So put your mind at ease and just enjoy each trip--you'll inflate again soon enough for the next one.