Can Feral/Alley Cats Get Too Old To Make Good House Pets?
Cats are incredibly adaptable creatures. They learn mainly in their younger years, before they are set in their ways. Sadly, many are abandoned every day through no fault of their own. Some are born to feral parents and know no other way to live.
Perhaps there is a stray (or feral) cat that you are thinking of adopting. If the cat is over five years old AND acts completely wild, avoiding all human contact, then the chances of being able to make a decent pet of the cat are very slim. They are better off being trapped, neutered and released back into the only life they have ever known.
How Wild Is That Cat?
Many feral or stray cats were raised as pets in homes with people and were simply abandoned. These cats, no matter what their age, WILL make good pets, because they have already learned that living indoors with humans can often be a good thing. These are the cats who walk right up to you, or will walk up to you given a few days or weeks of seeing you regularly.
These cats might act frightened, since they may have been abused, but they will also be openly curious about you, following you, maybe even begging food from you and rolling in the ground in front of you. They may let you pet them, but run of like a bolt of lightning when you try to pick them up.
A stray cat that acts like this can adjust to living indoors.
But if the stray runs from all people, will only eat any offered food when all people are gone and are over five years old, the chances are huge that moving indoors will terrify them. Cats can get phobias. It seems cats who have spent all of their lives outside under a big sky for five or more years are terrified of small confined spaces.
If You Want To Adopt Them Anyway
If you want to adopt this wild feral cat anyway, all power to you. Don't expect the cat to ever get affectionate with you or jump in your lap. They may spend months cowering behind the couch. They also will find it difficult (but not impossible) to learn to use a litter box. Here is a list of websites to help with some specific problems, but keep in mind they are mostly geared for cats under five years old.
If you are willing to put up with a cat like this, then go for bringing the cat in. Know that the cat will eventually have to go to the vet and get shots. If you already have cats, DO NOT bring in an older completely wild stray. They could be carrying illnesses like feline lukemia (FeLV) that are very contageous to your cats (but not to you).
If the cat goes into a panic attack (screaming, refusing to eat or drink, perpetual hiding, shaking, fainting) that lasts for two weeks, it's just not meant to be. It's kinder to let the cat go back outside rather than force the cat to stay in a place that clearly terrifies the cat.