> A key thing that must be remembered also is the smoothness of the rider.
I could not agree more.
By the way, the same applies to handlebars and stems.
My oldest 1972 Zapier Special still has the original stem&handlebar.
Cranks were replaced only because I found a pair that were not so worn
by the chafing of the shoes.
> It is important to examine your cranks,
Keep them clean, and inspect when cleaning.
As for stems and handlebars, don't let the clamp get loose and in need to be retightened. Never move around, never reset.
Sergio