Let me today talk to you about graha maturity years. These years are very useful in timing of events at simple glance of a jataka(horoscope). These year are very useful particularly in timing of Chara kaaraka replacements, fructification of fortunes(9th), Maturity of grahas etc.
The below table is qouted from Sri Pt. Sanjay Rath's, Crux of Vedic astrology. In that book these dates are particularly used in 9th house chapter for fructification of fortunes.
YEARS OF AFFECTING
Use in maturity, For example Mars matures at the 27th and 28th years. This could mean for example if a person is having Mangal dosha, The effects could be visible at the age of 27th or 28th year after birth. Hence, some Jyotisha's keep the opinion that Mangal dosha is not very effective if the person marries after the 28th year.
As another, example suppose a chart has Kaala Amrita Yoga where all other grahas are falling in path between Ketu to Rahu. This yoga causes the Nodes to be very dominant in the chart. An example which comes to the mind is the Charts of India and Pakistan. Both countries became an seperate nation in 14-15th Aug-1947. So the effects of nodes, particularly Ketu is very dominant in the chart. Now to see how long these effects will be dominant?. From the above table we see that Ketu matures till 41,42nd Year. So till the Years 1947+42=1989. We see in that year major political changes happened both in India and Pakistan. The Indian Congress party which held majority started to undergo changes from Nehru family dominance. And Pakistan General Zia dies in Plane crash.
Lets take another example of current US President Sri George W Bush,
We see that In his chart there is a chara Kaararaka replacement happening at the 17th degree, between Putra kaaraka Mars and Pitri kaaraka Mecury. From the above table we take the maximum primary year of these graha to see when the change will be completed. We see that the changes starts on 27th(Mars) age (1973) and is completed at the age of 32 ruled by Mercury(1977).
As per Wikepedia
Laura Welch met George W. Bush in 1977 at a backyard barbeque at the home of mutual friends. After a three-month courtship, she married him on November 5 of that year at the First United Methodist Church in Midland, the same church that she had been baptized in. 
Laura Bush is credited with influencing the maturation of her husband in the 1980s and with being one of the factors in his decision to stop drinking alcohol in 1986. 
Mercury is conjoined 7th Lord Saturn and 7th kaaraka Venus. Mars is on UL the Arudha for getting committed to someone. Hence these replacement bought about the Marriage and tremendous change in his life.
--Om Tat Sat---