why isn't it as hard?
blocked veins?
I'm the wrong person to ask, sorry.
I can tell you that I don't respond as if I was twenty five, in that there is smoke long before there is fire (meaning that I "feel" aroused long before I am "ready"), but I have compensated, by learning where all the muscles that help to control bloodflow are and I pay attention to the fluff level more than I used to. It takes more stimulation than when I was younger to keep things going, but nothing like what Peter describes.
My brother, two years younger than I am, had something like what you are describing and he went to the doctor and got Cialis. I haven't heard from him since. (kidding) He says it is great now.