Here I have 10% nic base in VG and some in PG, both oxidized very quickly, weeks. I say weeks because the specific bottles I speak of are more than 5 years old.
No off flavor of any perceptible kind, from myself, or others that are here using my juice. Sure, it's likely reduced in potency, so what at that level.
Now I also have some from a different vendor, purchased same time period @ 6% , discolored as well, not nearly as drastic as the 10%
Now mixing these down to something consumable, nearly non detectable color wise at 2.4% , at .3 it's clear as a bell in VG