Great, thanks for confirming.
I'll just lower it right before his events and set it back to the previous value after I've done the event, this way I'll be sure to not mess anything up.
My last playthrough was a while ago and memory is a fickle thing, but I believe that the value you mention for rare finds is derived from the game clock. If you set the timer and keep the code active, I'm fairly sure they would never refresh. Would be interesting to test.
Based on this theory, this could also mean that if you checked a store at a certain time and temporarily reset it to 0, it would take a long time for that store to refresh. For instance, if you're at 180 minutes of play time when you check and the store refreshes after 30 minutes, it will expect 210 minutes. If you reset it back to 0, you would then have to wait the full 210 minutes before that store would refresh.
Then again, I don't have access to the game code or have anywhere near your level of knowledge and I'm not basing this on any specific research, simply my own potentially unreliable memory.