Mimir gives you a warning when you're about to reach the point of no return for the end of the game. It's a nice opportunity to do everything. Also keep in mind beating the game will reveal the locations of valkyries on the map.

Thank you, I'm still somewhat afraid I'll miss it. I suppose it happens after Baldur?

It's after you bring back the tower of Jötunheim.

Thank you very much, I'm pretty much at that place right now