Fluffy Sally, I don't know how old you mean when you say very old....but my experiences with elderly cats has been that as they age, they tend to stay closer to home. Probably it has something to do with aching joints and loss of hearing and eyesight and they lose the confidence to stray from the building where they bed down at night.
I do hope, your family has provided for a sheltered place for your cat to sleep, like inside of a barn that has an actual bed made up for her.
My brother had a full time outdoor cat, but they still had a garage with a cat door, where the cat could escape to during bad weather or if a fox or something scared it.
Inside the garage, there was a bed for the cat, and in the winter my brother set up a heat lamp far enough above the bed to offer warmth but not so close as to cause the cat to get too hot. I think the smell of the garage dissuaded smaller predators from chasing in after her and bigger ones couldn't get through the small opening. On the same platform as the bed was where they gave the cat food and water.
There cat, in spite of being an outside cat still managed to live to be 22 years old. She' wasn't a friendly cat and my brother was about the only person who could approach her...but they did take the cat to the vet when needed and finally, took her to the vet when they felt she was having too difficult of a time to make it up and down the ramp 2 x 4 plank they installed next to the platform in order to help her in her older years when jumping up became to difficult to do.
Cats are not the bullet proof animals some people think they are and they can lose ears and tail tips from frost bites in the colder climates. If you live in a warmer area, there are still times when the weather is harsh...very hot or raining for days and it's just a good idea to have a safe place for your cat to go to get away from the worst of the bad weather, be it wet, hot, or cold.
I hope your kitty stays safe. I had an indoor outdoor cat, she could come and go as she pleased through the doggy door. One day she went out side and never returned and I never found out what happened to her. In my area, it's probable that either an owl, coyote, or raccoon got her.
I'm very glad to hear your kitty came back....and I hope she always will...
Stormy