...then don't say anything at all.
Do you guys abide by this age old adage when it comes to fan fic?
I am currently reading a fic that I started out really liking, but I feel like the actual writing is beginning to toe the line of being too pretentious. Up until this point the plot and character development have been phenomenal, but it's just kind of getting to a point where as a reader I am thinking "get on with it already!"
Several months ago I had started another fic that was a gahdzillion chapters long. The story started out great, fairly unique plot with engaging twists and turns...to a point. I stayed up until the wee hours of the morning and read to the fifty-leven-millionth chapter thinking that the story would circle back around to lead me closer to the conclusion about the opening scene in the prologue. Of course it didn't and I was furious...mostly at myself for hopping on the endless drama train.
Now if a story gets to a point that it is simply not my thing I have no trouble 'flouncing' it. But when I'm fairly invested and feel like it's been good up until a point and have even previously given the author reviews, I kind of feel like I should say something.
I think that I have the tendency to not review at all unless I have only positive things to say about the story. I realize it takes a lot guts for an author to put themselves out there, so I try not to be overly critical...but to what degree are you as a reader willing to speak your truth about what you think of an author's story when your opinion is not all rainbows & unicorns...?

P.S. This isn't my first time posting...but I do think this might be my first campfire :-)