You can edit different settings for a workers age.
#29: Editable Worker Age Settings
For the first time in the series, mod makers now have the optional ability to edit some of the age settings for workers. The four settings are:
Maturity Age: This is the age at which the worker loses the ability to naturally learn and physically improve faster than normal.
Decline Age: This is the age at which the worker starts to physically go into decline.
Relevancy Age: This is the age at which the worker becomes so out-dated that his entertainment skills start fading too.
Retirement Age: This is the baseline for their in-ring retirement; this does not guarantee that they retire at that age, only that it's when they start to consider it - it can be extended through certain circumstances, such as having a highly paid job, etc.
All of these values can either be filled in as an exact age or left to Random. The range of ages are the same as are possible in normal gameplay (i.e. Maturity Age can only be between 18 and 30, the same potential range as if it were left to random; this is because all of the game's internal calculations are based on that range, so if someone set it as 60, for example, you'd end up with ludicrously skewed values).
In previous games these values were calculated anew with each game that was started, using the worker's hidden Destiny value. That is still the case when the settings are left to Random, otherwise the game will use the settings the mod maker gave.