Maybe... But not because of flex.
I was surprised at the expense and difficulty I had in finding a square tapper compact crank when I wore out the rings on my old UNIVEGA. Sure, its taken me years to wear out my crank so its not something to do often.
So upgrading to a Hollowtech will not only make you feel better, in the future you will have a broader range of replacement cranks to choose from.
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No matter where you're at... There you are... Δf:=f(1/2)-f(-1/2)