As most of the time, I thinkCarl Watts wrote:
Err no actually this season is already a PB in terms of distance at the fastest average pace ever. 7500m+ a day at less than 2:03 pace all pretty much 17-18spm.
We all appear to need different forms of motivation if you want to continue rowing for a lifetime.
You never get faster or improve with age, don't kid yourself. If I had discovered rowing at 18 and in my early 20's I would now be looking back wondering how I ever did that pace. There is no way you "continue to improve" at 50 or else the rowing at the Olympics would be dominated by masters rowers.

Although its ofcourse fine it you like doing stuff you do now.
My point is, if you tell something, give context, which you did not, so I am doing it for you. Erging is very age friendly, relative speaking we can be pretty competitive as masters. Ofcourse after 40, potential will get less.
Like I said before, if you change your focus its possible to improve. Keep doing what you always did, yess thats a sure way to hit a wall.