Since triangles returned tooday, after a while playing my FPS become lower and lower until they start to inpact my game play. When they were first introduced I had the same issue, which stopped when they were removed. However as they returned now, the issue is back.
Here is two screenshoot of when I was streaming on osufrlive channel tooday, first is at the very first map, you can see FPS are at something like 290ish, and the second at the end of the stream 1 hour and a half later, FPS are 120ish. Later I played for a longer time, and when I closed the game fps where as low as 70ish FPS. Before triangles returned, I could play for as long as I wanted and FPS were always 300-270ish.
If you zoom on the images you can see the FPS counter, if you don't want to the 1st says 293FPS, the second 118FPS.
For comparaison, a screen of another end of stream yesterday when triangles were not back. You can see it's more than 2 yours after the start of the video, FPS were still 280ish