Certain portions of this document are Open Game Content, per the Open Game License. The Open Game License is attached to the end of the main page. All of the pages and text in the House Rules section is Open Game Content except any mentioned setting names (primarily Theralis and Forgotten Realms). Artwork and text in any other section is Closed Content. Open Content may be reproduced per the rules of the Open Game License. Closed Content may not be reproduced.
Please see the Open Gaming License for the appropriate legalese.
With levels taking years to achieve, the effects of age become important. The rules below cover aging for humans, and are somewhat harsh.
For every 5 years over 25, lose -1 DEX and -1 CON, and gain +1 INT and +1 WIS. If any attribute reaches 0 because of this, the character dies. STR and CHA are (usually) unaffected by age.
For each 1 year over 30, make a CON Check vs. DC 10. Every time this check is failed (a natural 1 always fails), roll one of the following Aging Effects:
1d20
1-3: STR -2 (muscle atrophy, bad back, weak legs, etc.)
4-6: DEX -2 (shaky hands, stroke, broken hip, etc.)
7-10: CON -2 (bad heart, weakened immune system, fragile bones, etc.)
11-12: INT -2 (memory loss, perception disorder, etc.)
13-14: WIS -2 (childhood regression, wandering mind, etc.)
15-16: CHR -2 (irascible, heightened fears, etc.)
17-18: Attack of Age! (permanent -5 hp; heart attack, ill winter, etc.)
19: Worsening Vision (-5 on all Spot and vision-related checks; taken twice results in blindness)
20: Hard of Hearing (-5 on all Listen and hearing-related checks; taken twice results in deafness)
Aging is harder on farmers than on nobles. Add the following bonus/penalties based on social class and environment. I don't use this, but I included it for completeness' sake.
Upper Class: +1 to CON for aging rolls.
Middle Class: no effect (merchants, sages, craftsmen).
Lower Class: -1 to CON for aging rolls.
Urban Setting: no effect.
Rural/Wilderness Setting: -1 to CON for aging rolls.
Malnutrition: Each season of a year you spend malnourished counts as a full extra year of aging.
Based on the above and some arcane spreadsheet lore, rural populations tend to break down like this (35% of the population consists of 4th level professionals or better):
Age: Population Percentage
Under 15: 41.5%
15-19: 12.2% (level 1-2)
20-24: 11.3% (level 3)
25-29: 10.3% (level 4)
30-34: 9% (level 4-5)
35-39: 6.7% (level 5)
40-44: 4.3% (level 5-6)
45-49: 2.5% (level 6)
50-54: 1.3% (level 6)
55+: 0.7% (level 7)
For more on the level breakdown shown here, see the Advancement Rules.