Ha, not only how much oxygen is in the bottle, but how much was absorbed while in tray. Developer won't survive long, one day. Fixer much more. Stop should be OK for long.
Look at your developer, if it is somewhat brown, is gone. Phenidon based developer will survive little longer than metol (PQ versus MQ).
But with fixer better count usage. It doesn't change the color, it doesn't change the smell. especially the one with hardener.