7.50 #maxage <age>
This maximum age for a monster. After this age it will
risk getting afflicitions and eventually die. Default is 50.
7.75 #startage <age>
The start age for a monster. Usually there is no need to
set this as it will be calculated automatically depending
on startage and skills. An age of zero clears this command
and an age of -1 sets start age to zero.
I think there is a typo in the latter description. I think it should read "dpending on maxage and skills". In my Anansi mod age didn't work correctly, but that might be because he's a shapechanger.