How quickly does beer absorb oxygen?

I can clearly see the post above yours. But it's not clear that that's what you were addressing when you said "The answer to the original poster's question..." For some reason, when you said "The answer to the original poster's question may be about a week..." I thought that part of your post was an attempt to answer the original poster's question. My bad.

BTW, the answer to "how long until oxidation becomes detectable?" doesn't have any one answer (even if everyone had the same palate), given all the variables. "About a week" is a shot in the dark.

In the meantime, in attempt to add value, here a couple of tangentially related presentations I did a while back:

Beer (In)Stability, Oxidation, and Freshness
Closed Transfers and other Cold Side Oxidation Mitigators

 

The negative (or positive) effects of oxygen on beer bottled with yeast will depend on the type of beer and the preferences of the person drinking the product. Trendy beers with big aromatic hop character will lose that character. Some bitterness will probably be lost in any beer. But my 30+ year homebrew poured clear and retained a mellow (but probably diminished) bitterness. Overall I didn't find any unpleasant flavors. I do acknowledge that these beers were never world-class brews, but their basic character, flaws and all, is retained. That can't be said for aged commercial beers that were packaged without yeast in glass or aluminum.