Grey Smudges on my iMac 27" Screen

I purchased an iMac 24" a couple of years back, after a month of purchase these grey smoke like clouds started to appear on the edges of the screen, so I contacted the service providers and the Display of my machine was replaced, but it turned out that this was a temporary solution, I started to have the same trouble once in every 2 months time, and every time they replaced the iMac Display, after many attempts Apple decided to replace my machine with the new iMac 27".

I had my fingers crossed that it won't happen again, but till date I am facing the same problem, and now after 3 attempts of replacing the iMac 27" Display, I am really fed up and frustrated. I told Apple that it is an internal hardware fault but they have an excuse saying it's an "environmental issue".

I read blogs and watched YouTube were people from around the world are complaining the same trouble, so I figured there can't be a global environmental issue.

They refused to replace my machine now, and I am not willing to replace the Display this time.

Apple is not ready to admit their fail in manufacture.

From years I have admired Apple and I buy all their products from a little iPod nano to the iMac as collectables, this is just not expected from them.

Please if anybody is facing the same issue, lets unite and fight for what is right.