There are two slight issues with further time travel as we currently understand it, both raised in the Twinning:

1. We apparently smashed the core mechanism for the Tower's time-travel abilities, and it exploded.

2. The post-dungeon recorded message indicates that only G'raha could survive the trip due to his bond with the tower, and nobody else could go with him.

So while it doesn't actually rule out further time travel, we don't currently have a time machine ready to take us wherever we want to go.



Also, changing the past gets even messier than changing the future - if we unwind time and make it so there was never a void, what happens to our history - to every voidsent we've ever encountered, and the entire Fifth Astral Era?

We would be creating a split in history so huge that it predates us by thousands of years.



Additionally, the Eden raids seem to be dealing with the Thirteenth in some way.