The planets that take a long time to move through a Sign show the long-term trends in a given area of life. They are important for forecasting the prolonged view of things. Because these planets stay in one Sign for so long, there are periods in the year when the faster-moving (short-term) planets will join them, further activating and enhancing the importance of a given House.
Jupiter stays in a Sign for about 1 year
Saturn 2 Vi years
Uranus 7 years
Neptune 14 years
Pluto 15 to 30 years