For a bunch of floor to ceiling windows, I have noticed extreme
pitting all over their exterior aluminum frames, far deeper than the
anodized layer. I think new window installation would cost a fortune
due to not fitting in the elevator, so I wonder where that leaves us.

I think the root cause is dirt and salt buildup that isn't flushed
due an overhang that protects from rain but not humidity (and not
enough cleaning). So say these are cleaned more regularly - will they
structurally hold up for many more years? Is there some kind of
treatment that would help clean, protect, or disguise?

And if needing replacement, would the whole gigantic windows have to
be replaced, or can you somehow stabilize the glass and unscrew the
frame parts for replacement? The windows/sliding doors are on a high
rise balcony, and function is more of a concern than looks. thanks