... I'm not trying to argue, I'm stating a fact - screens do NOT change tints over time. Your Air most likely has a worse yellowing screen issue than your iPad 4. But your iPad 4 still has the same "yellow screen issue" that it had since the beginning.
I beg to differ.... After 3 overnight sessions of my screen being left on with a white background and 100% brightness, my slight yellow tint in the bottom left has pretty much gone