I think people make a mistake by focusing this notion of "peaking".

I have a weight routine to make the most of my health and I cycle to work.
I make lists of books to read for professional usage and personal pleasure.
I try to improve my relationship with friends/family by being responsible and doing nice things for them, often from reminders I've left myself.

I don't want any year to be my "peak" but I want every year to be as full of life, growth & happiness as I can make it.
If I can't lift heavy at 90 I'll be lifting whatever I can for the greatest personal good.

It seems a much healthier attitude to just do your best and let be what will be rather than worrying about hills and troughs.