For me, this was after ~2 hours on a medium-sized map, this January. The game started out with about 20-30 fps, and ended as an unplayable slideshow, <10fps.
For comparison, I have never experienced such low frame rates on Zero-K regardless of unit count or map size, and the other player didn't complain either.
How many units did you have at that stage? We're finding games with 8 or more players a side can slow down after an hour; though this is because of the number of units present (often in excess of 4000).
For comparison, I have never experienced such low frame rates on Zero-K regardless of unit count or map size, and the other player didn't complain either.