I think I have something.
I made caravans bring 1,000 times the normal amount of items with the previous mod.
Before a caravan arrived, the game was running at about 200 FPS. After the caravan and diplomat had left, the FPS is still lingering at 95. While the caravan was here, it was around 50. I can post the save file if you think it would be helpful.
If you could, that would be helpful.
Also, let the diplomat in, and go through all his speech, he adds lag trying to pathfind to you infinitely if you don't let him in.
Having several years of data to see if it has a lingering impact is important, as well.
I have atom-smash tests complete.
I have a control save that runs at a usual 500-600 FPS around early spring. I am advancing my experimental save to the end of the year as well for the closest comparison I can make.
Atom-smash experiment after I have shut off the atom smasher, and eliminated the goblets seems to start the year bouncing around between 250 and 350.
I'm going to leave this running for a while longer to see if it will spike back up in the summer, or something, but in the meantime, I'd like to see if others get the same result I'm getting on the atom-smash test.
Atom Smasher Experiment saves on DFFDI'd like to see if someone else gets results on this test, as well, before I go announcing something.
EDIT:
I keep getting inconsistent readings on this, however.
First, I had a really slow game - 200 or so, but then, I end process the game, and reload the same save, and now, in the same season, I'm getting 400, and it's basically made up most of the FPS losses.
The same thing with those medium contraction tests - when I play back the same saves over and over, I lose all the FPS loss.
Maybe there's just a gremlin in the machine and so many variables beyond my control in this that I'm getting too much noise interfering making my data register false positives or false negatives when I should be getting positives, or else there actually is something about the way that the game is saved that "heals" the damage to the FPS that I've inflicted by doing all these tests. Perhaps the vectors are not repopulated in the same order between saves, and that is performing an inadvertent clean-up function which results in a FPS boost if you save, close the game, and then reload?