As a hypothetical feature of superhumanoid physiology, genetic manipulation, or a sci-fi explanation for improved longevity, yes.
"Is this possible even if implausible?" Yes, it is possible.
I'm not much of a mathematician, please forgive the loose mathematics to estimate an answer to "How much longer do they live?"*new info
The original calculations have been redacted in light of newer findings. You could estimate based on the tool at the bottom of this post a decrease in estimated age of 3 years for an 8% decrease in VO2 max (I've heard it quoted 1%/year in various clubs). The average is quoted as 40 for fitness enthusiasts and 24 for the average person in fitness and health clubs. Age affects oxygen-carrying capacity moreso than the other way around, and not as a given/established causal relationship, only as a correlation.
You could in the name of fiction form an estimate from those numbers, like, say "if a 150yo wanted a fitness age of 34 with a 208 heart rate, they'd need 150-34=116/3=38.67, so 40*1.08^38.67=40^19.6, a VO2 max of around 784" but you see how quickly that got out of hand. That could be the equivalent of a human with an elephant or whale's oxygen-carrying capacity.
The caveat to that is bigger isn't always better (think horses and cheetahs and dogs, which all have higher VO2 max than humans, with supportive anatomies for the levels they do have, and humans outlive all of them). I've never found a study that supported it, the dogs racing the Iditarod are said to be near 225 or 230 for VO2 max.
In science!-based reality, no. *Partial edit, somewhat more plausible, but still limited to the entirety of thenstructure supporting it. You'd need something like Greed from FMA's body structure (not Brotherhood).
"Even at elevations of 14,000 feet above sea level or higher, where the atmosphere contains much less oxygen than at sea level, most Tibetans do not overproduce red blood cells..."
Instead, they adapted to negate polycythemia, the body's response to oxygen deprivation (creating too many more red blood cells.
In an environment in which scientists (biologists) had anticipated higher red blood cell count to facilitate greater efficiency in oxygen-carrying capacity, humanity had instead adapted by way of genetics and interbreeding to mitigate the effects of hypoxia.
Human adaptation was thus primarily negating negatives (hypoxia & polycythemia) rather than bestowing positives (increased oxygenation, carrying capacity). Humanity adapts by nerfing environmental hazards moreso than outright buffing.
sphennings made an excellent point, results of studies do not necessarily mean a causal relationship between heart rate and lifespan. Athletes are the best example for both forced inclinations in oxygen-carrying capacity (supplements) and natural inclination of lower resting heart rates & higher oxygen-carrying capacity.
The base or resting heartrates of active individuals -- professional and elite athletes especially -- appears to inversely correlate with oxygen-carrying capacity measured as VO2 Max.
While this is estimated by scientists and doctors as the "common sense/advice" that healthy/fit individuals live longer, heart rate and oxygen-carrying capacity are -- I'm going to stop this here and finish the edit when I have a desktop in 4 days.
As per the above information on athletic correlation, I found
to disprove where I was originally going (that despite fitness and healthiness plenty of athletes die earlier than comparatively less fit or healthy individuals) but the more I search the more similar articles, journals, and studies I find.
This tool from the mercola article told me that despite my age, 34, and low VO2 max (31), my "real" count is actually <20 and about 59 for VO2 max. With the same max heart rate, it shows a loss of about 3 years & 8% VO2 max for picking the most sedentary choices. I tried with different info and it came out to be about the same.