Board Thread:Manga/@comment-39121488-20190413131938/@comment-25933225-20190414091649

For Keith Shadis, it has been explained many times. He isn't a reliable narrator: he met Grisha 18 years ago, in 832. Considering how old that event is, he might not remember the exact amont of years that has passed since. Another explanation could be: 18 is a number close to twenty, so he simply rounded 18 to 20, because he thought that precision wasn't necessary. Plus, he has chosen his words on the moment, he was improvising, it's not necessary to over-analyze each line he said. Grisha died in 845, 13 years after receiving his Titan.

For Uri, we don't know how old he was when he received the Founding Titan. But he was young (in his mid-twenty, probably). It was in 829. Frieda was 2 years old at this time. Uri was eaten in 842 (13 years after 829) by Frieda, who was 15 y-o. So, when Uri died, he was about 40 years old. Yes, he looked pretty old in the end, but this is the result of Ymir's curse: a shifter, on his last months, is weak, and might look older than he really is. The fact that Uri looked old in his fourties was the first hint for the fandom that shifters might have a limited life, long before Ymir's curse was revealed.

So, as far as we know, there is no known shifter that has lived over their 13 years-limit imposed by Ymir's curse.