Thread:CirUmeUela/@comment-27496405-20180307074410/@comment-26454055-20180527212630

Collider asked Infinity War screenwriters Christopher Markus and Stephen McFeely about the age of Thanos and they said "really old" but it sounds like it's not set in stone. That's in this video around 16:50

https://youtu.be/31hGnh7elAU