Adds "Old Age", a condition organic pawns and animals can receive on a birthday event when they are at least 95% through their lifespan (76 for humans). The Old Age condition will periodically cause an organic body part on the pawn/animal to receive the "Degradation" condition which will cause the part's efficiency to lower over time. At it's final stage, degradation destroys the part. The chance for degradation to occur is based on the severity of old age. At it's initial stage, degradation cannot occur. At it's final stage you could get degradation as frequently as once every 5 days. Degradation can only affect organic parts, so artificial/bionic parts are not affected by that condition. The same can be said for Old Age when it comes to non-organic pawns/animals so robots should be safe.
There are options for dealing with these conditions if you'd like to fight to keep your favorite pawns alive in their golden years. Both old age and degradation can be treated with medicine to slow them down or even reverse them (albeit slowly). Tend quality of 100% will stop the progression of these conditions and above that will slowly reverse them. Parts affected by degradation have some options depending on the part. Replaceable parts like limbs and some internal organs can simply be replaced via surgery. All parts can have a special nanite infusion done to cure degradation, though it requires medical skill 10 and 1 glitter-world medicine to perform.
This mod is intended to allow both pawns and animals to pass away naturally as they age. It's best used with pregnancy mods so that your colonists can repopulate as older members pass on. With Vanilla timescales you'll mostly notice it with animals that have relatively short lifespans but the mods's effects become much more pronounced when using it with a mod that alters aging speeds. It also works well with mods like Death Rattle. It was inspired by mods like Natural Death and Diseases+.