When did Guns 'n Roses become classic rock?

I was at a punk show last week. (The Epitaph tour, if anyone cares.) The band in discussion is called Escape the Fate. For starters, I should point out that this was an 'all ages' show. I used to go to all ages shows when I was 15. I am now almost 30. It really never occurred to me before I got there that the average age in the place might be 15. What made it bearable was good music and a decent bar with no one in line. Anywho, at one point during the evening I decided to ask these two girls standing next to me how old they were. They both told me they were 18 (probably being liberal on their lie.) One made the addition that she felt old in there. Obviously I pointed out that I was 29 and my friend was 32 and thus he could have been her dad (I do have a friend that has a 14 year old who is also 29 - this is a whole other story.)

As you all may or may not know, every respectable punk band has to have a cover song that is all punked out. These used to be songs like "Surfin' USA" (Pennywise), "Brown Eyed Girl" (Lagwagon), "Go Your Own Way" (NOFX), etc. Well Escape the Fate makes the following announcement: this song is for your mommys and daddys. They proceed to play "Take Me Down to the Paradise City" by G'nR. When did Guns 'n Roses become classic rock? I don't know. I should also point out that the oldest member in Escape the Fate was 21 tops.