It's not the length of time.
It's also the hypocrisy. The film makes a big deal out of the fact that Oswald did not have trial. It then mentions that Shaw was indicted for conspiracy to kill JFK. It does not even mention that he was tried and found not guilty. That is the height of hypocrisy.
There is no need to bring Clay Shaw into the JFK assassination. He had nothing to do with it.
fred