It is questionable what is, at present day, considered young and old (and particularly during mid-forties), as life expectancy doubled last century from roughly ~40 to ~80 years. which makes everyone in their forties old by ... olden standards and mid-life at current ones.

if we get to live through the (forthcoming or already unfolding) singularity, there's a fair chance new life standards extend to 140-180 years*, with medicine, yoga, nootropics** and all.

* https://en.wikipedia.org/wiki/Life_expectancy#Maximum ** https://en.wikipedia.org/wiki/Nootropic