I thought of replying to
this thread, but the forum tells me it's rather old. Also, it's about the Sony model. (AFAIK, they use the same screen tech, but why not use a forum that's about the same hardware I'm using :-)
Anyway.
When it's cold, the screen/ink starts to fade after a while, with every new refresh there is less black. I haven't (yet?) found out if it disappears altogether.
Once in the warm, it seems to "thaw" for a while (color getting stronger), then work as usual.
The temperature should be well within the storage temperatures - but how about actually using it when it's close to or even below zero (Celsius)?
Could that somehow damage the display?