Zodiac - sign not to watch!

So I saw this movie.....Zodiac which was based on the real case files of a serial killer in of course Amrica from the late 60's to the early 80's - the film starred "dreamy eyed" Jake Gyllenhall [as described by MSN Entertainment] and Robert Downey Jr [the same drug addicted one - very nice actor tho] and I would love to tell you why the film was made but I can't. My problem also is that the film is 2 1/2 hrs long - for an English film going nowhere, that's crazy!! Most people know I can't sit still for more than 30 seconds at a time.....during Salaam - E - Ishq - practically a 4 hr movie [I liked it tho], I started fidgeting after 3 hrs and shook the entire row along with me - Friend had to physically restrain me from creating semi-earthquake catastrophe!! Anyway, back to movie.....it started with people getting shot and carried on from there with no purpose. I mean, the case was never solved, a journalist got obsessed with it, got divorced coz of it, another journalist was driven to drink, it ruined a cop's life, and the man who supposedly did it was a pedophile, and liked publicity and so wrote cipher's with the 'Zodiac' alphabet [some vague medieval code - only interesting information in the whole movie], claimed responsibilities for murder's he apparently did not commit, stole his name and symbol from a watch brand.....Ok now it seems like I'm wandering but the movie is the same...there is no definite conclusion so I cannot figure out why they made it and that too, why they made it so long?? There is this episode of friends where Monica makes friend's with the woman who stole her wallet who does all sorts of crazy things coz she claims she lost 2 hrs of her life watching 'Dead Poet's society' [which I feel is quite a sweet movie by the way] - I currently feel the same!