I know I have already posted but I wanted to mention something else.

One thing that I think people have been overlooking myself included is that all of the suspects show a grudging dislike towards Patrick, I know this does not seem like much but I think it is perhaps one of the most significant clues we have.

It is quite clear that Red John does not hate Patrick, it is quite the opposite, Red John is quite fond of Patrick. Patrick is almost like family to Red John he has been a constant figure in his life for quite some time. There have been many occasions where Red John has saved Patrick and even reached out to him. Red John wants a friendship with Patrick something that is rather uncommon with all 6 suspects. I think that the need for further connection with Patrick also shows vulnerability, every time Red John is seemingly rejected by Patrick he kills, an act of defiance and rage, this makes me think that Red John is actually quite young, or was quite young somewhere in his 30s or early 40s now.

Personally I thought that it may be the sheriff but then I stated to realize that he does not fit the characteristics at all, the sheriff is seemingly kind hearted not to mention his age. I think that it is quite possible that Lisbon is working with Red John, it would make a lot of sense but I don't think it would make a good ending.

Think about the ideals of the show, it is about the constant presents of good and evil and the idea that evil can be overcome. Patrick has a warm and happy relationship with his team members. I honestly don't think that Heller would end it like that, the final message of the series and the reveal of Red John needs to be a powerful message, something that I don't think will be seen if Red John is someone to close to Jane.

On an unrelated note what do you think Patrick will do when he finds Red John?
I personally don't think he will outright kill him, because that concept very much conflicts with much of what Patrick stands for.