As I age, I think I'm kinda like a lake trout too - I keep growing rounder and so far my fertility is still going strong !!!!
As far as retention - Generally, I agree, that releasing breeders is a better option USUALLY.
But ..... there are some situations, specific to watersheds where maybe a few years (either sequentially or in proportion) where low water levels, spawning conditions, etc.. have created lower recruitment levels (less new fish surviving) and, as a result, may have removed/reduced an age class (in population distribution)..... this may change what retention plans might look like.
That's were having enough resources to monitor our watersheds is money well spent. More BIOs should mean better fisheries and resource management.
There is also the general condition that exists (outside of fishing pressure alone) where the trophic status of lakes move sup the scale (generally) the further south you move - basically warmer more productive and rich water allowing fish to grow faster.
This is also true and prevalent and well studies in SASK - age studies on Walleye prove this to be true for us too.