Plateaus make for easy riding!

Ed, what's going on with the swimming?  What's your goal?  I'm not sure exactly how to answer your question other than to give you my personal thoughts on "improving" my fitness.  

I'm not saying that there should be absolutely no expectation of improvement, but if everyone continually improved at what they spend time on then we would all turn pro eventually, right?  I haven't been riding my bike on a regular basis for years on end, but I know that even when I was training for RAGBRAI and riding a lot, I never really got any faster than averaging around 17-18 mph on the bike.  One of the reasons that the Tour de France impresses me so much is that the winner averages almost 25 mph over the course of the 2500+ miles, and that includes all of those ridiculous mountain stages.  I can't average 20 mph for 15 miles on a flat course.  If I REALLY wanted to improve my bike speed, I suppose that there are things I could attempt to do it (i.e. building leg muscle by lifting, sprinting on the bike, etc) but I'm pretty content with how fast I go.  

Which leads back to my original question: what's the goal for wanting to swim faster?  When I workout my goal is simply time for the most part.  If I rode my bike significantly faster, for example, I would need to lengthen my courses to get in the same amount of time.  Even training for RAGBRAI my goals were based on distance and not necessarily how fast I could cover the miles.  I don't have a problem with you wanting to swim faster, but rather identifying WHY you want to be faster might help.  

If it's what you want to do, then I would get into a Masters Swimming class.  I've heard people talk very highly of the stroke technique help that you can get from someone who's qualified to coach adults in swimming.  I'm sure stroke technique is probably at least part of it.

Brad may argue differently based on his comments in the past about exceeding physical limits and the power of the mind, but I also think that every person DOES have a natural limit to athletic ability.  I hate to say it, but you and I are in our 40s and not getting any younger.  

I'm incredibly impressed with the fact that you can swim 2500 meters in an hour.  If you ever want to feel like Ryan Lochte, just come to San Diego and go for a swim with me.  Remember, last May I took 13 minutes to swim 400 meters in a sprint tri.