My DA-7 display requires a minor adjustment after a few minutes of warming up. Indeed, if I get the contrast knob set at JUUUUUUUST the right spot, it can be readable through the range from boot-up to fully-warmed up and I don't HAVE to adjust it. But there is a noticeable warm up and darkening/increase in contrast to the LCD display, over the first few minutes as it warms up.

I always thought that was largely independent of the heat of the other components, though. I was under the impression that that was just the LCD screen itself, warming up - and the display would behave that way regardless of the heat coming off the other components in the board. Maybe not.

I have an old Roland synth with a similar LCD display that does the same thing (and it has a corresponding contrast knob, as well). Turn it on and, in the first few minutes, you have to crank the contrast knob all the way up to be able to read the screen. A bit after that though, it becomes too dark and unreadable and you have to then turn down the contrast.

Like the DA-7 display, if you just leave the contrast setting alone after powering off, when you first start it up, the screen will be too light/bright but, it will warm up and eventually get to the same contrast as the last time it was warmed up and then you can see everything, just fine.