How long it takes to get to Saturn depends on a variety of factors, such as the particular path and speed of a spacecraft. These factors can account for the differing lengths of time taken by the past different space missions to Saturn.
For example, by using the gravitational assist of Venus, the Cassini mission took seven years to get to Saturn. In 1997, this mission left Earth and entered Saturn’s orbit in 2004. However, it took the New Horizons mission less time to get to this planet. This mission left Earth in January 2006 and reached Saturn's orbit in June of 2008. The New Horizons mission traveled at a faster launch speed, and this is one factor that accounts for the difference in time length between these two missions. Likewise, for different missions such as Voyager 1 and Pioneer 11, it took different amounts of time to reach Saturn.