Also don't forget the Medical science of the time is far in advance of what we've got. The book with loads of information about Terra IIRC says that 60 is basically no real age at all and that you could live far longer, have multiple careers etc and still be over 100 when you pop off this mortal coil.
Considering the whole racehorse/dog/cat pedigree breeding system the Clans have, as well as the Scientists actively eliminating genetic defects etc, then I don't see why a Clan Trueborn couldn't live for a very long time. Sure nothing approaching what the rumoured life expectancy of Belters (which may in some cases be 200+ if not in essence, ageless, although such a thing would be amazingly tightly controlled), but still longer than what we have now and remaining fit and healthy. At 84 most of us would probably not really be safe to drive a car if we're honest, and would probably need help going on long walks to the shops etc. Natasha K was driving Mechs and commanding battlefield forces without it even slowing her down apparently.
But the big problem is that its a Clan trueborn, and they don't expect to live long, indeed they actively seek out dying gloriously. The Clans abhor waste, but their warriors are basically disposable and the biggest problem for a Clan Warrior is that they are a Clan Warrior and the society they live in.