The Game of Thrones series has already started going beyond the books with the latest season and it's only a matter of time when they reach the end and now we might know how much time we have. Also there's some exciting information that might excite you. Recently HBO president Michael Lombardo talked with reporters regarding the popular series and when he was asked about when the series would end, this is what he said:

Seven seasons and out’ has never been the conversation. The question is, how much beyond the seventh season are we going to do? I think [Benioff and Weiss] are feeling there's probably 2 more years after [season] 6. As I've said before, I'd always love for them to change their minds, but I think that's their plan right now.

When he was asked about plans for a spinoff, he suggested about a prequel, though he didn't give any confirmation regarding the prequel.

I would be open to anything David and Dan want to do … there’s enormous storytelling to be mined in a prequel. The focus is on figuring out the next few years of this show.