The other issue with "a huge token window" is that if you fill it, it seems like relevance for any specific part of the window is diminished - which makes it hard to override default model behavior.

Interestingly, recently it seems to me like codex is actually compressing early and often so that it stays in the smarter-feeling reasoning zone of the first 1/3rd of the window, which is a neat solution for this, albeit with the caveat of post-compression behavior differences cropping up more often.