We're meant to infer that Maechen (SPOILER)has met the real Lenne, which of course means he's been to the real Zanarkand that was destroyed 1000 years previously. Which makes him a little over a thousand years old. But being unsent has its advantages, apparently.

On a related note, he could most likely cross between Spira and DZ, like Auron and the Fayth of Bahamut. I wonder if he ever did.