I wouldn't recommend a balanced food / booze production though. Stockpile it to the limit, it doesn't go bad.
this, however, is definitely no good (I was recently called out for screenshotting my having 1000 plants as having too many in a 30-dwarf fortress), FPS loss is caused by units first then items
To quantify the effect of item count on FPS, I loaded up a recent fort with over 50,000 prepared meals, about 524 barrels of which are in a QSP, and let it run for a week or so for FPS to stabilize. It bounces up and down a bit, but seems to mostly be around 32
I then spawned some magma on that tile using DFHack to destroy the QSP load. Unfortunately, most of the meals were in green glass pots, so only about 20,000 were able to be destroyed in this simple way. The smoke cleared, and I let it run for another few days for FPS to find a new equilibrium while viewing the same part of the fort, was interrupted by the game pausing as a dwarf went insane, and again as he claimed a workshop. But the FPS readout at the top did not increase, rather it stayed fairly consistent at 32.
Assuming that the number of items does indeed negatively impact FPS in a substantial way, it appears my particular fort has long ago crossed some threshold where that negative impact has reached a limit whereby further increasing the item count no longer matters to FPS. There are excesses in every stock category, so destroying 20,000 may not have been a relatively large enough reduction to see any effect on the overall item calculation load. Given the current state of this particular fort, amassing prepared meals does not appear to effect FPS. Reducing meals from 50,000 to 30,000 had no measurable effect anyway.
Ammo is by far the biggest line item in the stocks menu at 105,727 (only 5,328 stones due to a very lucrative mechanism trading scheme), so some more magma was spawned, and ammo was reduced to 22,217. The fort was left to run for some more days, an artifact steel warhammer was created, a buzzard monster was riddled with 5 pages of marksdwarf arrows, and again, no effect on FPS was observed. Based on this test, in my wildly unstable and inconsistent fort, the number of items appears to have little to no impact on FPS (100,000 total items melted, FPS constant at 32). I suppose the next step would be to flood the whole fort with magma... But well over 50% of the total item count in the stock menu has already been destroyed, so I wouldn't expect to see any significantly different results from that.
How much of an impact do you think item count has on FPS in general, and how did you come to that conclusion?
I suppose it could be an irreversible effect, and once items have been created, the FPS is thereafter penalized, no matter if that item is subsequently destroyed or allowed to remain.