Span of a person's life
On the Discworld the span of a person's life is not measured by how long they lived, but by their actions. It is said that a person is not truly dead until the things they set in motion while alive have stopped, and the effects of their actions are over. When the clock that they wound up winds down, when the crops they planted are harvested, then a person is dead.
Despite having been killed and buried in five graves, Suffer-Not-Injustice-Vimes' memory and legacy lived on, so that even three hundred years later, people were wary about trying to become king of Ankh, recalling the part axes played in the death of the last one.
It is also said that 'while a man's name is still spoken he is not dead'. On Roundworld people still know and speak of Julius Caesar, William Shakespeare and Winston Churchill, decades or even centuries after their death. The Clacks operators have taken this one step further with the policy of 'sending home' and putting the name of dead clacks men on the overhead, with orders to turn around and resend when it reaches the end of the line, so the name will travel forever on the clacks lines.