It's unusual for Cornish X's to live that long, but as long as they are doing well, I see no problem with this at all. It's only keeping them alive
if they are unhealthy and suffering, that could be seen as wrong. The long-lived ones mentioned in this thread seem like they're doing just fine.
I have had CX's that lived quite awhile, some hens I bought form a guy way back when I first started keeping chickens. I had no idea then what they were, they were just
big. I treated them the same as my others, they free ranged and ate layer crumbles. They laid enormous brown eggs, lots were double-yolked.
Eventually, they started dropping dead of CHF. I don't know how old they were, they were already laying when I got the. I had them at least 6 months, but that was about 15 years ago, I don't recall exactly. When the last one showed signs of CHF, we decided to butcher her. She dressed out to around 15 lbs, so she probably weighed at least 20, live.
CalebtheChicken, she was nowhere near 5 feet tall.
Not even close to 3 feet tall.
A lot of people have kept these birds to see how long they'd make it, usually because they got attached to them, and just didn't want to eat them. Results are mixed, some do pretty well,
most don't live a whole year. Results will vary greatly with diet, climate, what strain they came from, how much exercise they get, etc.