Okay, here is my thought on the matter:
I think that the original rentheads are not those who have seen it x amount of times or with so-and-so starring in it or who know all of the words to La Vie Boheme (sorry Jen!). I don't think being an "original" renthead is a title you can achieve. To me you only have to look at the word original to get your answer. Correct me if I'm wrong, but the term "Renthead" was created for those who were there from the very beginning, who started seeing the show off broadway and followed it to where it is today. They were the ones who were there in those first couple of rows every night, keeping the show popular and the seats filled.
Personally I love the show and the OBCR and I think the OBC was amazing. I absolutely get the message of the show, I do know all of the words, I do know lots of useless trivia, but I would not call myself a renthead. Nor would I call my sister, who has seen it many, many more times than I have (I only saw it once), a Renthead.
I totally agree with Kato 1 that "the title doesn't apply anymore. it stood for something that does not and cannot exist anymore, that was specific to that time period, the cast(s), the feelings about the show. it was different than it is now."
That said, I do think you need to see the show, whether on broadway or on tour, to feel the full impact. Personally I enjoyed the movie, but there were parts taken out and others added and I think to really appreciate Rent you need to see it performed.
The truth is, whatever we call ourselves we are all fans. So just go enjoy the show and forget about what you call yourself or what your friend calls his/herself.
"I wrote a book: "How to Be Popular". Now I've put together a top ten list of how to help you:
-Elphie, everyday... shower. I mean, who knows? Maybe some of that green is gonna come off!
-Deodorant Elphie. No body likes a stinky witch!
-I think we've covered the hair, we'll get to that.
-Clean underclothes. That's all I'm gonna say.
-Look at your posture. That's no way to be popular!
-Bed made, room straightened. We've done that.
-Colors blended. Oookay.
-But the most important thing to have, to make yourself popular, is to keep your beautiful smile."
~Kristin Chenoweth in her last performance of the song "Popular"