Does the passage of time affect my kittens?

I know that kittens gain skill over time. But do they actually age? And can they die of old age? Or will my kittens as long as I provide them with enough food continue to live and gain skills?

It seems to me they don't die of old age. I am in year 93 now, and from year ±20/30 no kittens died I think. My first kitten still has an age of 16, and I know for sure I have her for longer than 16 years. (Her skill level is proficient 20%, and I was keeping track of her skill increase.) I didn't check what her age was before, but because I have had her for longer then 16 years, I am quite sure the age does not reflect 'real' age in-game.

Because I've had that one for so long, and another for sure too, I believe the kittens do not die of old age. Luckily, otherwise the skills would reset every time a kitten die of old age.

update: Year 96, and Lily Paws is still a sixteen year old farmer. Only change is the skills: she is now 25% proficient.

update 2 Furthermore, In the village.jsthere is the following line:

this.age = 16 + this.rand(30);

when the new kitten is constructed (alongside with the creation of the name). In the rest of the code I cannot find anything where this age does anything at all.

update 3 Year 152. Lily Paws is still a sixteen year old girl, enslaved on my farm. Evil laugh

update 4 Year 202. I think I can confirm that Lily Paws is immortal. She is still busy on the farm. She mastered the job though, so she has that going for her, which is nice.

update 5 Year 327. Anyone doubting the immortality of Lily Paws is an idiot. She still is a 16 year old. Possibly sucks the blood out of innocent canines in the neighborhood.