I just wonder if this happens to all good monitors (Eizo, LaCie, NEC) used for professional colour editing. It might only be related to cheap monitors like Dell, as they do not have as much electronics to boost the colour and brightness fast.
I have an Eizo monitor and from checks I have done, it needs at least 30 mins to become stable. My old cheap one would need a full hour. I think it all depends on how much the electronics and illumination system are rated . I would expect better quality monitors to have components working well within their full capacity and use components that are inherently more stable.
It seems like wasting a lot of time to start working with pictures.
Just leave it on all the time like me
Terry