As far as shoulders and pressing...
I have talked to a few older lifters, ie: 50 and up and quite a few of them have seemed to come to some kind of agreement that at a certain point, certain parts of the body seem to give up on any progression (from a natural stand point anyway) A few of them even told me I might rather suddenly start to digress in even my best lifts. But I always seem to think of guys like Freddie Peterson, who at 73 hit a #680 DL.
I truly still feel I can hit a new high in deads yet, as that exercise was probably never pushed to an all out best when I was in my youth. I really believe I could have reached a #700+ DL without any drugs in my 20's or 30's if I was doing it with a complete mental focus on the work and effort and hitting huge singles. In my youth, I was more of a higher repper in the lower extremeties legs hips and almost always put my efforts into singles in pressing and BP's.(Lifts a sucked at actually)
Nowadays, the response from the shoulders and chest are always limiting and (only guessing) nerve output, along with fiber growth, pathways, etc. etc. ability to recover at a higher level and keep that momentum going, is nearly impossible for me. I never wanted to believe it, but many older guys just do not press what they did in their youth and knee and low back problems limit any kind of heavy pulling or squatting. I am gifted in the knee and low back area thus far, but who knows!?
Rowing and other pulling work for me, is pretty stable and it kinda baffles me how I can still improve some in those type exercises.
I really have no other way to explain it, as everything I have tried in pressing movements, make absolutely no difference, or at best, have me only keeping status quo, up and down. Whereas pulling recovers, stays at a higher level if I put in enough work and does still show some signs of progression.
I do however realize that at some point, no matter what one does, the highest PR gains and abilities, will all slowly be behind me.