The core message is that animal years map very badly to human years.
During the first twenty years, we are busy with development. The fertility part is gender specific, and lasts about 25 to 30 years in women and much longer in men. Conflating active years with fertility is a problematic idea. Maturity is a very fuzzy concept, but cortical development is commonly not considered complete until the mid-twenties. The variance in energy is probably higher compared across different individuals than across different age groups. Health problems also vary greatly from person to person, but it's fair to say that crossing 40 risk factors for everything go up dramatically.
How many active years humans get out of their life is subject to great individual variation. Some get zero. Others are highly productive for 60+ years. But I agree it's not enough - that's why we need transhuman advances in science. Less than a Guard of Terra, maybe more like a Space Marine ;)