iMac LCD smudge number of repairs before replacement

[MrXiro]

I'm asking out of curiosity more than anything... but as my iMac got the under the glass LCD screen smudge after only 3 months of usage and nothing has changed in my apartment since, I'm going to assume it will happen again 3-4 months after I got it replaced at the Apple store.

How many times will I have to have this problem fixed before Apple says, "here take a new one."?

This is also known as a Lemon Policy at various retailers.

I'm in Los Angeles, CA if there is a state by state rule...