User blog comment:B214/Volume 22 spoilers/@comment-29778526-20170126060633/@comment-9595671-20170127011524

10,000 is more of an average I think, it's possible that some Devils likely live longer than that. I think Zekram for one example might be one of the few who are atleast 10,000 years in age since he's the First Bael.

Plus life-spans do change, and considering how strength is an important factor to Devils, I'd say the stronger you get, the longer you'll likely be able to live. That could be one reason Odin's still kicking despite his current age, he's still strong enough to stay alive.

And luckily, while the seal itself will hold that long, the seal only needs to keep Trihexa contained inside of it, if they find a way to kill ofd Trihexa for good before than during that timeframe then the others will get the chance to see them again too.