[A3] Aging

Each creature has a "physical" and a "mental" age.
Mental age is the actual time the creature has been conscious; i.e. nothing affects mental age except the flow of time.
Physical age is the age of the body of the creature, this can be affected by the flow of time or magical effects.
For each race, a maximum age is listed (in [P2?] for PC races, monsters use [M?]). The age categories for each creature is determined from the max.age, as follows:
Age Category: Child Young
Adult Old Venerable
Age Code: C Y A O V
Minimum Age: 0 .2 x Max .4 x Max .6 x Max .8 x Max
Physical Age Adj.: Str: -1 0 0 -1 -2
Dex: +2 0 -1 -1 -2
Con: +1 0 0 -2 -4
Cml: 0 0 0 -1 -2
Move Rate: -3 0 0 -3 -6
Mental Age Adj.: Int: +1 0 0 0 -1
Wis: -2 0 +1 +2 +3
Chr: -1 0 0 +1 0
NonWeapon Prof.: -4 0 +4 +8 +10
Thus, for a human (Max.age=100): Child is 0-19 years, Young Adult is 20-39, Adult is 40-59, Old is 60-79, and Venerable is 80+.
There are circumstances (hierophant druids, time elementals, undead status) that modify the maximum age for a creature. In this case, the age categories are modified accordingly (but the creature would not "instantly" change age categories due to this, it would take a great deal of time).
If a creature's physical age exceeds his maximum age, he dies of natural causes, but can be raised by magical or psionic means. But he he soon die afterwards (within a few days) unless means to reduce the physical age of the creature (such as a Potion of Longevity) is found.
If a creature's mental age exceeds his maximum age, he dies of mysterious causes, and is PERMANENTLY dead. Wishes, Artifacts, even Divine Intervention will not bring the creature back under any circumstances. The spirit has gone through the vortex in Concordant Opposition (and can never be reached, even with the Speak with Dead spell) or (by choice of his diety) has been Reincarnated as another life form. In the latter case, all memory and experiences of the former life are lost (actually, they become a small part of the creature's diety).