I know of older ones, but am not exactly sure of their ages.
For the record, my first "anthro" experience was at a Gen Con back in 1975. I fell in lust with a drawing of an anthro vixen character in the art gallery. No one else in my group had the same reaction. I also remember gong to a Gen Con and there were only four cosplayers. Three Star Trek characters and a Klingon.
My first Sci-Fi Con was in 1975, San Mateo, CA if I remember right. Sci-Fi Cosplayers, Star Trek Cosplayers, a few Furry-based space characters, four(4) Start Trek blooper reels. One lady was doing an Orion Slave Girl cosplay, green makeup and all. I thought she might have had professional help with the green stuff - looked too professional to me. that's all I remember of my first Sci-Fi Con. Might even have been a Trekker Con, it's been that long ago.
Old age sux.
As an aside, there was a Con at the Marriott in San Jose, CA one year and the staff was having a fit because several females were wearing mostly body paint and prosthetics. Signs went up everywhere to the effect of "Do Not Sit on the furnishings if you are wearing body paint!" That was the day of the parade and two of them are standing in front of me and my wife who's acting as my handler. One's painted like a leopard, the other like a tiger.
Besides prosthetics, paint and hair coloring that must have been pro quality, they're wearing the skimpiest of thongs, painted to blend in, tails that were glued on(!) and the kind of pasties photographers use. We've seen them walking around since early so being polite, I ask what brand of paint they're using, since it seems to be holding up well. The leopard lady says "PAX paint." PAX paint is made from equal parts acrylic paint, the tube stuff and Pros-Aide Adhesive!!! You need a special serious level remover to get this stuff off!!! She then says "It won't rub off." and proceeds to rub the shit out of her arm to prove a point. It stayed right there, no smudges She then says they have a quart of Pros-Aide remover in their room and they planned to take all day Monday after the Con to remove the paint. Yikes.
BTW, they never made the parade; Con officials asked them not to march with the rest of us since they weren't exactly 'G' rated. Spoilsports. I had my camera ready to get the reactions of the audience as we went by them. They let the d00ds in the full rubber horse costumes wearing bondage gear to march, though. Go figure.
I am from a Native American tribe of what you might call OG furries... some of us have animal names. We recently lost the oldest member of our tribe, Crow. I think he was in his 90's. His whole house was decorated with crow-themed things. He loved cartoon crows. He may not have been involved in the fandom, but I don't think you need to be. Sometimes it's cool to just enjoy cartoon critters.
There have been furries who died of old age, so that basically covers the the human lifespan. I know one in his 70s, but he isn't the oldest.
It can also be tricky to determine who does and doesn't qualify as a furry. Was it really necessary to belong to a particular social circle 40+ years ago to qualify? I'd say no, as people have liked humanoid animals for millennia, but others might disagree.