Fnancial advisor, F2, for reference, and checking all my units for "extra cost units" and as far as I can tell it's indefinitely. You might want to count your Extra Unit Costs in your saved games and see if they match the reports in the F2 screen too, see if it's only mine or yours too that do that.
As for Caching, it persists over saves and recalcs and loading a completely different save game and then this one again, so should have passed any caching issues?
Oh, for checking it, train a Storyteller and build a building with him, and see what the Extra Costs post says before training, after training but before building, and after building, to see if it all does what it should (meaning first 0, or actually in my save 7, then +1, and then down to 0 again).
A older save of mine (about 2 months maybe) does not have this issue it seems, but it has the supply line issue, meaning it has "invisible units" counted towards supply line costs with a total of (checking F5) in Friendly Territory (if they count towards Supply too): 5, Neutral Territory: 56, Enemy Territory: 17, Barbarian Territory: 32, for a total of 110, but Supply line is counting 140 active units outside of Domestic area and paying for all but the free cost ones.
Also an issue I've had before and reported but not fixed.
Supplying that save too here now. I am not actively playing it as I think I overextended my computer, or the game limits a bit, so the turns were too long and MAF's started happening.