But what happens after years of doing external you reach a peak, then you start going down the other side of the peak. Externals are based more on conditioning, so as you get older you get slower and weaker and soon people with a less experence are giving you a hard time or showing you up.
Nice overgeneralisation.

At 56, I guess must still be climbing the peak and expect to do so for a while yet.

Actually, you can learn to use your leverage and sensitivity better with experience. A lot of BJJ guys start off with a fast, athletic game, and as they get older they move to a slower, tighter game that requires less strength and speed and can still vanquish the twentysomething athletes.

Then if you are lucky you meet some little guy and by using little effort can throw you around like a piece of hay, and just laugh. Then you know there is something missing.
Ive met several guys like this. My BJJ instructor for one, JJ Machado another. Gogen Yamaguchi was rumoured to have such attributes in his extreme old age according to one eyewitness I know personally. "External" martial artists one and all., although Tim Cartmell (an internal martial artist, look him up) says he thinks BJJ is internal.