Tim Gillett wrote:Drift? In what parameter(s) and to what degree? What would cause that?
A good question - to which I cannot really answer with much authority, as I am no expert.
I would guess it's like with any machinery: it depends on both the specific technology used, the characteristics of the components used, the operating environment and its changes (termal effects, for example) and how much the technology and design can/has accounted for all these factors in the cost range. An example is the backlighting tech or the time and thermal stability of the dye used for LCD displays. Or clocks. All clocks drift, some more than others.
So there are displays that are extremely stable and don't change or change minimally over time, and some that change relatively quickly. On a single display, it may be hard to spot because of the lack of references, but if you have two or three near each other (like I've had for basically the last two decades), it can be pretty evident. One of the reasons I recently went to the 49" ultra-wide :)
In general, color is hard if one wants precision - one of the reasons for which reference monitors are insanely expensive, I guess.
You find a bunch of stuff if you google something like "display calibration drifting" or similar.