According to the Flash TV series, Eobard Thawne/Reverse Flash (born 2151) has come back from the 22th century to kill Barry/The Flash in the 21st century.
Eobard mentioned that he wanted to kill Barry because he hated future Barry. That means Barry is STILL ALIVE and kicking in the 22th century. Let's calculate how old that makes him:
He finished high school at 17 probably as most US kids.He finished at the Uni at 21 or 22, depending on the university. Let's stick with 22, forensics is hard to learn . After that he went to work with CCPD as their forensics/analyst guy. He looked like a well established guy in his current workplace and every colleague in that department seemed to know him to some degree. Let's assume that another 2 years, which would make him 24 at the time he became the Flash (2014). That makes him 25 in 2015.
Eobard looked like a 40 something guy,but he lived 15 years in the past. So when he left the 22th century he was around 30. 2151+30=2181. We know Barry is still alive in that time because Eobard told us so.
That makes Barry 191 years old. Unless the Speedforce grants longevity as well I don't see how that's possible. On top of that his metabolism is crazy fast which would make him age faster rather than slower in real life (I think).
I was surprised at Barry not freaking out on that when Eobard told him? On the other hand Barry doesn't seem to be portraied as a particularly bright guy in the series. Most of the time he acts very childish and immature for his age. At certain situations he completely lacks common sense.
Maybe in season 2 it will suddenly dawn on him: Oh my GAWD I'm a grandpa!!! XD