Only Seven or Eight Seasons?

In a recent Vanity Fair interview with show runners D.B. Weiss and David Benioff, some very important information about the future of Game of thrones was uncovered.  As the show's speed increases at an ever increasing rate, the possibility that the show would pass George R.R. Martin and his books has become a real problem.  Just in case this problem would come to fruition Benioff told Vanity Fair that they have taken certain precaution:

Last year we went out to Santa Fe for a week to sit down with him [Martin] and just talk through where things are going, because we don’t know if we are going to catch up and where exactly that would be. If you know the ending, then you can lay the groundwork for it. And so we want to know how everything ends. We want to be able to set things up. So we just sat down with him and literally went through every character.

Although, it should come as no surprise with an entire book in the A Song of Ice and Fire series not even started that George would be unable to paint an entire picture for the show creators.  When asked about the subject George told Vanity Fair:

I can give them the broad strokes of what I intend to write, but the details aren’t there yet. I’m hopeful that I can not let them catch up with me.

Benioff and Weiss told Vanity Fair that they are shooting to have the show run seven to eight seasons in length.

It doesn't just keep on going because it can, I think the desire to milk more out of it is what would eventually kill it, if we gave in to that.

As we approach the premiere date for season 4 we can see that some of the story lines will jump as far ahead as A Dance with Dragons (book 5).  With that known could we expect to see the show spoiling events for book readers in season 5?  Let me know your thoughts in the comments below.