The average life span of an indoor cat is much longer than that of an outdoor cat. I understand why outdoor kitties have their place, like at my rural relatives' houses. Those kitties are loved and cared for, but they're really more working animals; keeping the rodent population under control. But for someone who wants a mostly non-working kitty, indoors is totally the way to go.

I even found this chart, for estimating the relative "human" ages of indoor and outdoor cats.

I'm glad Griffin and Sham-Wow get to live a safe life. I hope all the SAHD's get a chance to live as dangerously as they choose someday. 

My indoor/outdoor guy is around 12. He's got scars. I'd love to keep him in, but he's honestly not comfortable using a litter box for pooping. Like if we go away overnight, there will just be pee. Two days of being inside, he'll have managed to do the deed but he's ready to go out and make sure the other cats have stayed off his lawn, and take a nice constitutional in the potato field. He also came to us as an outdoor cat who hung out at various houses. Now we are his permanent home with occasional short visits to the neighbors - I met a lady last week who was so happy to see him alive, it made my day. Both because she had a nice story about him and also (selfishly) he's stopped going down the hill. 

@WhatWouldJohnCrichtonDo?, I had to do a little math because your chart didn't go high enough. Our 21 year old cat that we had to put down last year was the equivalent of a 100 year old human.

13 hours ago, Maggie Mae said:

He also came to us as an outdoor cat who hung out at various houses

I rescued a cat who had come into my then work once...was never able to make her an indoor cat, the hardwiring was already there.  I miss her.

Both of my wee dudes were previously homeless/semi-feral so they HATED being kept indoors. When the bird flu panic happened dude number two was still alive and had to be kept in to stop him from getting hold of possibly infected birds. Never in his whole life did he wreck the house other than that one week. Both of them didn't like going for a wee inside the house, even with a litter tray. The oldest one only got neutered when he came to live with us so a lot of the territorial/roaming behaviour kinda stuck, he used to chase other cats and the occasional fox off his patch and the one time we put him in a cattery for a week he came back and wandered round howling at stuff for days. I miss those wee goofballs, they were like weird hobos who moved in with us and had battle scars and interesting quirks.