My mistake, it's true your physical performances will degrade over time. But these malus will be compensated with bonuses for some mental skills.
Besides, it seems that the longevity is not affected by your physical condition. The core mechanic to influence that is your resource of "Spirit" (you mostly loose it when you get killed).
Posted By Caspian
Each skill in the game requires the use of one primary attribute, and up to two secondary attributes for a maximum of three. As you age, some skills naturally atrophy at a faster rate while others become easier to develop. Strength, Agility, and Stamina all become more difficult to maintain while Will, Reason, and Focus become easier. For social skills, it’s about half and half. Persuasion becomes harder to level (nobody listens to their elders), while both Intuition and Leadership become easier.
This change in attributes creates an interesting game dynamic. Those characters built solely around the physical skills will find they’re most effective in their youth. It’s during this time they are more likely to be out adventuring, risking their lives in the wilderness, or traveling as a merchant on dangerous highways.
At some point those physical activities will become more difficult. You’ll find you’re less able to hold your own in fights against the younger, more virile characters. This is part of the natural order.
In contrast, you’ll find skills that rely on your willpower, or prolonged focus, become significantly easier. You’ll be able to spend more time and become more effective in research and hobbies that require a keen eye. If you were able to build a kingdom, your venerable character will become more influential as your Leadership reaches an all-time high.