Day 1: Let's pick components (that includes the screen)
[technology advances]
Day 120: Oh, crap, the screen isn't fully compatible with the rest of the components -or- that particular model has a fault that will be too obvious and detrimental to our product, must use a different one.

Because technology advanced, the new screen will have slightly blacker blacks, slightly better colours, it will consume slightly less electricity, the pixel's changes to fail will be slightly less and so on. The new screen is better because it's chosen in day number 120, that's all.