Investigations are what happen where there reasonable belief that crimes may have been committed based on information already available.
The GOP thought Benghazi was worth 4 years of investigating.
You are missing an important difference. After 10 months there was evidence of a crime. Hell after 30 seconds of investigating there was evidence of a crime with Hillary's emails.
After 10 months they are no closer to "the truth". So how long does the investigation have to go on for before Democrats will let it go? 1 year, 4 years, 8 years?