if you apply theoretical stuff like relativity to everyday examples it is easy to oversee factors that really count, and I personally think you should to make the calculation possible.
However in this case the simplification has gone too far.
I real life you age much faster when you fly a lot. This is due to the combines efects of sleep loss, radiation, low humidity, jet lag, rapid climatic changes, bad food, warm beer, chaep wiskey etc. etc. etc. . . . . .
Nice work theo`s, talking about nanoseconds while overseeing the years. Find a formula that includes the above facors. Good luck
Sq