Far as we know our girls are around 13 and still going strong. One sometimes acts like she might be getting a touch hard of hearing, but inconsistently enough we’re not sure...other than that, they both act like kittens. I wish I could say the diet was something special but it’s whatever kibble is on sale any given week because that’s what we can afford.
I don’t doubt your cats enjoy it, and it’s most likely very good for them as well, but I’ve seen cats who had the best of care decline at 10, 11 and the cat versions of hardcore skid row cases who made it to their upper teens or even 20+.
I suspect genes have more to do with it than we like to think...
With the present economy, my money is very short, too-but I live in the country-I can always barter my labor for tiling a backsplash or I can bake a couple loaves of wholegrain bread for trade to a neighbor who has chickens for eggs, or a fresh free range hen, plucked and cleaned, including neck and innards for my cats and my Husky to have with their dry and canned food...
Although I buy my canine companions from a reputable AKC kennel, the opposite is true for the feline ones-I’ve never had a cat that was not a rescue-they don’t seem to have the genetic problems of purebred felines, and live long healthy lives-one exception was an orange tabby I adopted as an adult-the vet said he’d had a major head injury early in his life-he had seizures sometimes the first two years we had him, and was always somewhat fragile-he died of a brain tumor last year, but he was estimated to be about 15.