I think it would nice if we could keep playing after we reach a victory condition. I just finished my first game (Lumeris, soooo much dust), and I won by score victory. I wanted to keep playing to check out a few things but it wouldn't let me. Since its a score victory there's no point in loading an earlier save and trying to go longer. I will cut off that victory method in the future though. 

Tek

Yes this needs to happen.

I played Sophons had the same feeling at the end of turn 126.  I wonder if sandbox mode might be different.

I played as Sophons as well. Sandbox mode is literally the easiest mode so it's not worth looking into until the release I guess. I used the guide to deactivate Score Victory that I found on Steam but my game ended after ~115 turns by a military victory though I didn't eliminate the other remaining empire (Lumeris). Was planning on spreading the other pops throughout my empire for the approval bonus from the Colonial Rights system upgrade.

Yes, I think when we choose endless game mode we can keep playing until all the enemy done, so we can discover all the technology, feel the power of the strong fleet and find all the interesting things in the game.  I know now we can play 250 turn when we choose endless game mode, but it still not long for me :D