REAL REASON TRASH STOPS SPAWNING (Mambo Loa)
I've tested this multiple times, and truth is, trash does not stop spawning on the 30th or 100th day, those are rumors.
The trash stops spawning the day after you've picked up the 100th pile of trash even if you've already sold some piles, the count stays the same.
We have more cheats and tips for this game here, The Urbz : Sims in the City cheats
Comments for this hint