well, if it makes you feel better about yourself, then, yes, I'd call it "more flexible" butt, as you get older, the flexibility will tend to be more of a droop. {It sucks to get old!}
I have the same issue, though I hesitate to call it a "problem". I'm 46, so I'm not a kid, but mine arcs up and stays there when I'm turned-on, although it does seem to lose a bit of that rigidity when I get into the later rounds on a good night of fucking. The negatives for me are that the Reverse Cowboy is basically out of the question for round one, since that position bends my cock down towards my knees and it does not want to be bent like that. Doggie is fine since I can lean over her and use that angle. Any face-to-face position works fine, but having her on top is best, and I've been told that I'm curved like a G-spot vibrator, so they seem to really get into that position.
I can relate about being really hard. Sometimes when getting oral, they keep trying to bend it over to point straight out, and that isn't really very pleasurable either, and you can't keep telling them not to do that.
Overall though, I've heard many more positive comments about how it's so hard all the time, and that outweighs the adjustments to positions that I have to make. And they always get a good laugh when we're cleaning up and I hang a towel on it.